en: In the past decades many density-functional theory methods and codes adopting periodic boundary conditions have been developed and are now extensively used in condensed matter physics and materials science research. Only in 2016, however, their precision (i.e., to which extent properties computed with different codes agree among each other) was systematically assessed on elemental crystals: a first crucial step to evaluate the reliability of such computations. We discuss here general recommendations for verification studies aiming at further testing precision and transferability of density-functional-theory computational approaches and codes. We illustrate such recommendations using a greatly expanded protocol covering the whole periodic table from Z=1 to 96 and characterizing 10 prototypical cubic compounds for each element: 4 unaries and 6 oxides, spanning a wide range of coordination numbers and oxidation states. The primary outcome is a reference dataset of 960 equations of state cross-checked between two all-electron codes, then used to verify and improve nine pseudopotential-based approaches. Such effort is facilitated by deploying AiiDA common workflows that perform automatic input parameter selection, provide identical input/output interfaces across codes, and ensure full reproducibility. Finally, we discuss the extent to which the current results for total energies can be reused for different goals (e.g., obtaining formation energies). This data entry contains all data to reproduce the results, as well as the resulting curated all-electron dataset and the scripts to generate the figures of the paper.

en: How to verify the precision of density-functional-theory implementations via reproducible and universal workflows

automation

display_name: automation

dft

display_name: dft

equation-of-state

display_name: equation-of-state

pseudopotentials

display_name: pseudopotentials

verification

display_name: verification


$oid: OBSOLETE

en: Due to their remarkable properties, single-layer 2-D materials appear as excellent candidates to extend Moore's scaling law beyond the currently manufactured silicon FinFETs. However, the known 2-D semiconducting components, essentially transition metal dichalcogenides, are still far from delivering the expected performance. Based on a recent theoretical study that predicts the existence of more than 1800 exfoliable 2-D materials, we investigate here the 100 most promising contenders for logic applications.

en: 2‐D materials for ultrascaled field-effect transistors: one hundred candidates under the ab initio microscope

materialscloud

approval_status: approved

en:
Materials Cloud is a platform built to enable the seamless sharing and dissemination of resources in computational materials science, offering educational, research, and archiving tools; simulation software and services; and curated and raw data. These underpin published results and empower data-based discovery, compliant with data management plans and the FAIR principles.

In the Materials Cloud you can browse, explore, download, or deposit raw and curated data (in the Discover, Explore, and Archive sections); you can access cloud or redeployable simulation services (from AiiDAlab turnkey simulations to the Quantum Mobile virtual machine, the AiiDA registry of plugins and workflows, and the OSSCAR notebooks, in the Work section), and you can use all our educational material, tutorials and lectures (in the Learn section).

en: Materials Cloud

de: Materials Cloud

fr: Materials Cloud

it: Materials Cloud

political_level: other

state: active

type: organization

psi

capacity: public

type: dataset

key: guid

key: uri

value: DCAT Harvester Materials Cloud

envi

de: Umwelt

en: Environment

fr: Environnement

it: Ambiente

ab-initio-device-simulation

display_name: ab-initio-device-simulation

cscs

display_name: cscs

performance-comparison

display_name: performance-comparison

prace

display_name: prace

snsf

display_name: snsf


en:
The JuHemd (Jülich-Heusler-magnetic-database) is a collection of the magnetic phase transition types and transition temperatures (Tc) for experimentally documented Heusler and Heusler-like materials, as found by density functional calculations augmented by the Monte Carlo method, and as reported by experiment in the literature.
The database contains results on 400 compounds, many of them with different setups of the chemical order/disorder, totaling 776 systems. The ground state electronic structure was obtained by density functional theory calculations with the JuKKR code. Two exchange-correlation functionals were employed: the local density approximation (LDA) and the generalized gradient approximation (GGA). The chemical disorder was treated within the coherent-potential approximation. For 306 materials (627 systems) with sizable magnetization, the Heisenberg exchange parameters were evaluated using the method of infinitesimal rotations and the Tc was determined by our in-house Monte Carlo program. The simulated data for all the compounds in the database are accompanied by experimental data published in the literature: the crystal structure, the lattice constant, the Tc and the character of the magnetic phase transition. The correlation between the experimental reports and the results for LDA and GGA functionals and the statistical analysis of these results will be published elsewhere.

en: The JuHemd (Jülich-Heusler-magnetic-database) of the Monte Carlo simulated critical temperatures of the magnetic phase transition for experimentally reported Heusler and Heusler-like materials

critical-temperature

display_name: critical-temperature

density-functional-theory

display_name: density-functional-theory

erc

display_name: erc

heusler-alloy

display_name: heusler-alloy

jlvmd

display_name: jlvmd

juhemd

display_name: juhemd

kkr

display_name: kkr

magnetic-phase-transition

display_name: magnetic-phase-transition

magnetic-structure

display_name: magnetic-structure

max

display_name: max

monte-carlo

display_name: monte-carlo


en: The renormalization of electronic eigenenergies due to electron-phonon coupling (temperature dependence and zero-point motion effect) is sizable in many materials with light atoms. This effect, often neglected in ab initio calculations, can be computed using the perturbation-based Allen-Heine-Cardona theory in the adiabatic or non-adiabatic harmonic approximation. After a short description of the recent progresses in this field and a brief overview of the theory, we focus on the issue of phonon wavevector sampling convergence, until now poorly understood. Indeed, the renormalization is obtained numerically through a slowly converging q-point integration. For non-zero Born effective charges, we show that a divergence appears in the electron-phonon matrix elements at q → Γ, leading to a divergence of the adiabatic renormalization at band extrema. This problem is exacerbated by the slow convergence of Born effective charges with electronic wavevector sampling, which leaves residual Born effective charges in ab initio calculations on materials that are physically devoid of such charges. Here, we propose a solution that improves this convergence. However, for materials where Born effective charges are physically non-zero, the divergence of the renormalization indicates a breakdown of the adiabatic harmonic approximation, which we assess here by switching to the non-adiabatic harmonic approximation. Also, we study the convergence behavior of the renormalization and develop reliable extrapolation schemes to obtain the converged results. Finally, the adiabatic and non-adiabatic theories, with corrections for the slow Born effective charge convergence problem (and the associated divergence) are applied to the study of five semiconductors and insulators: α-AlN, β-AlN, BN, diamond, and silicon. For these five materials, we present the zero-point  renormalization, temperature dependence, phonon-induced lifetime broadening, and the renormalized electronic band structure.

en: Temperature dependence of the electronic structure of semiconductors and insulators

ab-initio

display_name: ab-initio

allen-heine-cardona

display_name: allen-heine-cardona

electron-phonon-coupling

display_name: electron-phonon-coupling

first-principles

display_name: first-principles

temperature-dependence

display_name: temperature-dependence

zero-point-renormalization

display_name: zero-point-renormalization


en:
Enormous research efforts are currently devoted to the discovery of 'perovskite-inspired materials', aiming to replicate the astonishing optoelectronic performance of lead-halide perovskites (LHPs). Recently, chalco halides of group IV/V elements have attracted attention due to the stability provided by stronger metal-chalcogen bonds, alongside compositional flexibility and ns2 cations — a performance-defining feature of LHPs. Following the experimental report of stable, solution-grown tin-antimony sulfoiodide (Sn2SbS2I3) solar cells, with power conversion efficiencies above 4%, we comprehensively characterise the structural and electronic properties of this emerging material. We find that the experimentally-reported centrosymmetric Cmcm crystal structure represents an average over multiple polar Cmc2_1 configurations. This dynamic crystal structure and ferroelectric behaviour could benefit photovoltaic performance. Using state-of-the-art ab initio methods, we assess the efficiency limits of this material, finding maximal solar-conversion efficiencies η_max > 30 % with film thicknesses t > 0.5μm, at the radiative limit.

Open-access Materials Horizons paper: https://doi.org/10.1039/D1MH00764E
Talks on this and other works at: https://www.youtube.com/channel/UCoVGnBeZeWmKzv8_-PzCKCw

en: Hidden spontaneous polarisation in the chalcohalide photovoltaic Sn2SbS2I3

chalcohalide

display_name: chalcohalide

defect-tolerance

display_name: defect-tolerance

earth-abundant

display_name: earth-abundant

epsrc

display_name: epsrc

ferroelectric

display_name: ferroelectric

lone-pair

display_name: lone-pair

perovskite-inspired

display_name: perovskite-inspired

photovoltaic

display_name: photovoltaic

polarisation

display_name: polarisation

symmetry-breaking

display_name: symmetry-breaking

thin-film-photovoltaic

display_name: thin-film-photovoltaic

vasp

display_name: vasp


en: Perovskite yttrium tantalum oxynitride is theoretically proposed as a promising semiconductor for solar water splitting because of the predicted bandgap and energy positions of band edges. In experiment, however, we show here that depending on processing parameters, yttrium tantalum oxynitrides exist in multiphases, including the desired perovskite YTaON2, defect fluorite YTa(O,N,o)4, and N-doped YTaO4. These multiphases have bandgaps ranging between 2.13 and 2.31 eV, all responsive to visible light. The N-doped YTaO4, perovskite main phase, and fluorite main phase derived from crystalline fergusonite oxide precursors exhibit interesting photoelectrochemical performances for water oxidation, while the defect fluorite derived from low crystallized scheelite-type oxide precursors show negligible activity. Preliminarily measurements show that loading IrOx cocatalyst on N-doped YTaO4 significantly improves its photoelectrochemical performance encouraging further studies to optimize this new material for solar fuel production.

en: Yttrium tantalum oxynitride multiphases as photoanodes for water oxidation

computational-screening

display_name: computational-screening

marvel

display_name: marvel

oxynitride-perovskite

display_name: oxynitride-perovskite

solar-water-splitting

display_name: solar-water-splitting


en: This entry provides the atomic structures of three bulk amorphous TiO2 models generated through the melt-and-quench method with different cooling rates and of ten O-O peroxy linkages obtained by adding two holes to the bulk model constructed with the lowest cooling rate.

en: Intrinsic defects in amorphous TiO2

bulk-model

display_name: bulk-model

holes

display_name: holes

peroxy-linkage

display_name: peroxy-linkage


en: This record contains the experimental and computational data needed to support the work done on on-surface synthesis of conjugated polymers consisting of indeno[2,1-b]fluorene units, which are antiaromatic and open-shell biradicaloids. The observed reaction products have been characterized via low-temperature scanning tunneling microscopy/spectroscopy and noncontact atomic force microscopy, complemented by density-functional theory calculations. These polymers present a low band gap when adsorbed on Au(111). Moreover, their pronounced antiaromaticity and radical character, elucidated by ab initio calculations, make them promising candidates for applications in electronics and spintronics. Further, they provide a rich playground to explore magnetism in low-dimensional organic nanomaterials.

en: On-surface synthesis of antiaromatic and open-shell indeno[2,1-b]fluorene polymers and their lateral fusion into porous ribbons

antiaromatic

display_name: antiaromatic

density-functional-theory

display_name: density-functional-theory

nics

display_name: nics

on-surface-reactions

display_name: on-surface-reactions

polymers

display_name: polymers


en: Molecular simulations are computationally expensive, especially in systems with multiple free energy minima. To address this problem many enhanced sampling techniques have been developed. Metadynamics uses a bias potential defined as a sum of Gaussian hills in space of few (one or two) collective variables. This bias potential disfavors states that have been visited since the beginning of the simulation. Multiple walker metadynamics simulates the system in multiple parallel replicas. The bias potential disfavors states that have been visited since the beginning of the simulation in any replica. Flying Gaussian method presented here also simulates the system in multiple parallel replicas. It disfavors states that are, at certain moment, similar in two or more replicas. It was demonstrated on Alanine Dipeptide in vacuum and water, cis/trans-isomerisation of Proline-containing peptides and Met-enkephalin.

en: Free-Energy Surface Prediction by Flying Gaussian Method

enhanced-sampling

display_name: enhanced-sampling

free-energy

display_name: free-energy

metadynamics

display_name: metadynamics

molecular-dynamics-simulation

display_name: molecular-dynamics-simulation


en: We determine the transition levels of electron and hole polarons at the BiVO4–water interface through thermodynamic integration within a hybrid functional scheme, thereby accounting for the liquid nature of the water component. The electron polaron is found to be less stable at the interface than in the bulk by 0.18 eV, while for the hole polaron the binding energy increases by 0.20 eV when the charge localizes in the surface layer of BiVO4. These results indicate that interfacial effects on the polaron binding energy and charge distribution are sizeable and cannot trivially be inferred from bulk calculations.

en: Electron and Hole Polarons at the BiVO4–Water Interface

materialscloud

en:
Materials Cloud is a platform built to enable the seamless sharing and dissemination of resources in computational materials science, offering educational, research, and archiving tools; simulation software and services; and curated and raw data. These underpin published results and empower data-based discovery, compliant with data management plans and the FAIR principles.

In the Materials Cloud you can browse, explore, download, or deposit raw and curated data (in the Discover, Explore, and Archive sections); you can access cloud or redeployable simulation services (from AiiDAlab turnkey simulations to the Quantum Mobile virtual machine, the AiiDA registry of plugins and workflows, and the OSSCAR notebooks, in the Work section), and you can use all our educational material, tutorials and lectures (in the Learn section).

molecular-dynamics

display_name: molecular-dynamics

polarons

display_name: polarons

water-splitting

display_name: water-splitting


en: The morphology, interfacial bonding energetics and charge transfer of Ni clusters and nanoparticles on slightly-reduced CeO2-x(111) surfaces at 100 to 300 K have been studied using single crystal adsorption calorimetry (SCAC), low-energy ion scattering spectroscopy (LEIS), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and density functional theory (DFT).  The initial heat of adsorption of Ni vapor decreased with the extent of pre-reduction (x) of the CeO2-x(111), showing that stoichiometric ceria adsorbs Ni more strongly than oxygen vacancies.  On CeO1.95(111) at 300 K, the heat dropped quickly with coverage in the first 0.1 ML, attributed to nucleation of Ni clusters on stoichiometric steps, followed by the Ni particles spreading onto less favorable terrace sites. At 100 K, the clusters nucleate on terraces due to slower diffusion. Adsorbed Ni monomers are in the +2 oxidation state, and they bind by ~45 kJ/mol more strongly to step sites than terraces. The measured heat of adsorption versus average particle size on terraces is favorably compared to DFT calculations.  The Ce 3d XPS lineshape showed an increase in Ce3+/Ce4+ ratio with Ni coverage, providing the number of electrons donated to the ceria per Ni atom. The charge transferred per Ni is initially large but strongly decreases with increasing cluster size for both experiments and DFT, and shows large differences between clusters at steps versus terraces. This charge is localized on the interfacial Ni and Ce atoms in their atomic layers closest to the interface. This knowledge is crucial to understanding the nature of the active sites on the surface of Ni-CeO2 catalysts for which metal-oxide interactions play a very important role in the activation of O-H and C-H bonds.  The changes in these interactions with Ni particle size (metal loading) and the extent of reduction of the ceria help to explain how previously reported catalytic activity and selectivity change with these same structural details.

en: Ni Nanoparticles on CeO2(111): Energetics, Electron Transfer and Structure by Ni Adsorption Calorimetry, Spectroscopies and DFT

materialscloud

en: Materials Cloud

envi

en: Environment

ni-charge-transfer

display_name: ni-charge-transfer

ni-heat-of-adsorption

display_name: ni-heat-of-adsorption


en: The bifunctional mechanism for the oxygen evolution reaction (OER) involving two distinct reaction sites is studied through the computational hydrogen electrode method for a set of catalyst materials including rutile TiO2(110), anatase TiO2(101), SnO2(110), RuO2(110), IrO2(110), Ni2P(0001), and BiVO4(001). The calculations are performed both at the semilocal level and at the hybrid functional level. Moreover, anodic conditions are modeled and their effect on the OER free energy steps is evaluated. The free energies of the reaction steps indicate that for specific combinations of catalysts, the limitations due to the linear scaling relationship can be overcome, leading to smaller overpotentials for the overall OER. At the same time, a detailed analysis of the results reveals a strong dependence on the adopted functional. For both functionals, it is shown that the energy level of the highest occupied electronic state can serve as a descriptor to guide the search for the optimal catalyst acting as a hydrogen acceptor. These results support the bifunctional mechanism as a means to break the linear scaling relationship and to further reduce the overpotential of the OER.

en: Oxygen evolution reaction: Bifunctional mechanism breaking the linear scaling relationship

bifunctional

display_name: bifunctional

epfl

display_name: epfl

interface

display_name: interface

linear-scaling

display_name: linear-scaling

oer

display_name: oer

overpotential

display_name: overpotential

oxygen-evolution-reaction

display_name: oxygen-evolution-reaction


en: A widespread method of crystal preparation is to precipitate it from a supersaturated solution. In such a process, control of solution concentration is of paramount importance. The nucleation process, polymorph selection, and crystal habits depend crucially on this thermodynamic parameter. When performing molecular dynamics simulations with a fixed number of molecules in the canonical ensemble, crystal growth is accompanied by a decrease in the solution concentration. This modification of the thermodynamic condition leads to significant artifacts. Inspired by the recent development of the constant chemical potential molecular dynamics simulation method by Perego et al. [J. Chem. Phys. 2015, 142, 144113], we develop a spherical variant of it to study nucleation from solution. Our method allows determining the crystal nucleus size and nucleation rates at constant supersaturation. As an example, we study the homogeneous nucleation of sodium chloride from its supersaturated aqueous solution.

en: Molecular Dynamics Simulations of Crystal Nucleation from Solution at Constant Chemical Potential

erc

display_name: erc

nucleation

display_name: nucleation

nucleation-kinetics

display_name: nucleation-kinetics

solution-crystallization

display_name: solution-crystallization


en: The pathway of the oxygen evolution reaction at the Pt(1 1 1)/water interface is disclosed through constant Fermi level molecular dynamics. Upon the application of a positive bias potential H2O_ads and O_ads adsorbates are found to arrange in a hexagonal lattice with an irregular alternation. Increasing further the electrode potential then induces the oxygen evolution reaction, which is found to proceed through a hydrogen peroxide intermediate. Calculation of the associated overpotential shows a reduction of 0.2 eV compared to the associative mechanism. This result highlights the forcefullness of the applied scheme in exploring catalytic reactions in an unbiased way.

en: Reaction pathway of oxygen evolution on Pt(1 1 1) revealed through constant Fermi level molecular dynamics

constant-fermi-level-molecular-dynamics

display_name: constant-fermi-level-molecular-dynamics

oer-mechanism

display_name: oer-mechanism


en: A good hydrogen storage material should adsorb hydrogen in high concentrations and with optimal binding energies. Exohedrally metal decorated carbon fullerene structures were proposed as a promising material in this context. We present a fully ab-initio, unbiased structure search of the configurational space of decorated C60 fullerenes and find that many of the hitherto postulated ground state structures are not ground states. We determine the energetically lowest configurations for decorations with a varying number of decorating atoms (2 ≤ n ≤ 32) for alkali metals, alkaline-earth metals as well as some other important elements and find that the dense uniform distribution of the decorating atoms over the surface of the C60 , desired for hydrogen storage, can be obtained only for a few elements. An understanding of the behavior of the decorating atoms can be obtained by analyzing their bonding characteristics via the electron localization function.

en: Stable structures of exohedrally decorated C60-fullerenes

elements

display_name: elements

exohedral

display_name: exohedral

snsf

display_name: snsf


en: This repository contains the PLUMED-2 input files required to generate the data used in the ITRE publications. ITRE is a method to reweight Molecular Dynamics trajectory biased with a history-dependent potential (such as Metadynamics), and calculate unbiased thermodynamic observables. Since it uses the trajectory itself as a proxy of a grid, its scaling does not depend on the dimensionality of the space explored. In addition, thanks to its formulation, it is less affected by out-of-equilibrium points that characterize the early stages of a biased calculation and are usually discarded. Thanks to this feature, it can be used to increase the statistics when evaluating a thermodynamic observable from biased calculation.

en: Iterative unbiasing of quasi-equilibrium sampling

enhanced-sampling

display_name: enhanced-sampling

molecular-dynamics

display_name: molecular-dynamics

statistical-mechanics

display_name: statistical-mechanics


en:
Molecular mechanics potentials for small molecules suffer inaccuracies. To apply corrections we used a concept called property map to calculate corrections. It was calculated as a sum of [correction_i exp(-lambda D(x, x_i))] divided by the sum of [exp(-lambda D(x, x_i))], where correction_i is the difference between the accurate and inaccurate potential for i-th landmark structure x_i, lambda is a chosen prefactor, D is a distance (e.g. RMSD or MSD) and x are atomic coordinates. The concept was tested on alanine dipeptide (all combinations of 7 force fields, one used as a model of accurate and one as inaccurate). Next it was applied on an anticancer drug Imatinib (General AMBER Force Field corrected to DFT).
Simulations were carried out in Gromacs 2016.4. DFTB/MM simulation was carried out in CP2K 7.1. Correction was Implemented using Plumed 2.4. DFT energies were calculated by ORCA 4.0 at the BP86/def2-TZVP level of theory.

en: Property map collective variable as a useful tool for force field correction

dft

display_name: dft

free-energy

display_name: free-energy

molecular-dynamics-simulation

display_name: molecular-dynamics-simulation

molecular-mechanics

display_name: molecular-mechanics


en: In this work we demonstrate the on surface synthesis of  nonacene and heptacene and we discuss their open shell character comparing experimental evidence to theoretical predictions. The record contains input files to reproduce the calculations discussed in the manuscript and the raw data of the experimental images discussed.

en: On-surface light-induced generation of higher acenes and elucidation of their open-shell character

materialscloud

en:
Materials Cloud is a platform built to enable the seamless sharing and dissemination of resources in computational materials science, offering educational, research, and archiving tools; simulation software and services; and curated and raw data. These underpin published results and empower data-based discovery, compliant with data management plans and the FAIR principles.

In the Materials Cloud you can browse, explore, download, or deposit raw and curated data (in the Discover, Explore, and Archive sections); you can access cloud or redeployable simulation services (from AiiDAlab turnkey simulations to the Quantum Mobile virtual machine, the AiiDA registry of plugins and workflows, and the OSSCAR notebooks, in the Work section), and you can use all our educational material, tutorials and lectures (in the Learn section).

ab-initio

display_name: ab-initio

gw

display_name: gw

on-surface-synthesis

display_name: on-surface-synthesis

scanning-probe-microscopy

display_name: scanning-probe-microscopy


en: Recent experiments show that the CoCrFeNiPd high-entropy alloy (HEA) is significantly stronger than CoCrFeNi and with nanoscale composition fluctuations beyond those expected for random alloys. These fluctuations were suggested to be responsible for strengthening. Here, a recent parameter-free theory for initial yield strength in fcc random alloys is shown to predict the strength of CoCrFeNiPd in good agreement with experiments. The strengthening is due mainly to the large misfit volume of Pd in CoCrFeNi, indicating that the effects of the non-random composition fluctuations are secondary. Analyses of strength variations and strengthening-associated length scales help rationalize why dislocation motion is insensitive to such fluctuations. These findings point to the value of theory for understanding the mechanical behavior of HEAs.

en: Origin of high strength in the CoCrFeNiPd high-entropy alloy

materialscloud

en: Materials Cloud

epfl

display_name: epfl

high-entropy-alloys

display_name: high-entropy-alloys

palladium

display_name: palladium

solute-strengthening-theory

display_name: solute-strengthening-theory

yield-strength

display_name: yield-strength


en: We screen a database of more than 69,000 hypothetical covalent organic frameworks (COFs) for carbon capture, using parasitic energy as a metric. In order to compute CO2-framework interactions in molecular simulations, we develop a genetic algorithm to tune the charge equilibration method and derive accurate framework partial charges. Nearly 400 COFs are identified with parasitic energy lower than that of an amine scrubbing process using monoethanolamine; over 70 are better performers than the best experimental COFs; and several perform similarly to Mg-MOF-74. We analyze the effect of pore topology on carbon capture performance in order to guide development of improved carbon capture materials.

en: In silico discovery of covalent organic frameworks for carbon capture

envi

en: Environment

cofs

display_name: cofs

computational-screening

display_name: computational-screening

covalent-organic-frameworks

display_name: covalent-organic-frameworks

erc

display_name: erc

gas-adsorption

display_name: gas-adsorption


en: Many low-thermal-conductivity (κL) crystals show intriguing temperature (T) dependence of κL: κL∝T-1 (crystal-like) at intermediate temperatures whereas weak T-dependence (glass-like) at high temperatures. It has been in debate whether thermal transport can still be described by phonons at the Ioffe-Regel limit. In this work, we propose that most phonons are still well defined for thermal transport, whereas they carry heat via dual channels: "normal" phonons described by the Boltzmann transport equation theory and "diffuson-like" phonons described by the diffusion theory. Three physics-based criteria are incorporated into first-principles calculations to judge mode-by-mode between the two phonon channels. Case studies on La2Zr2O7 and Tl3VSe4 show that normal phonons dominate low temperatures while diffuson-like phonons dominate high temperatures. Our present dual-phonon theory enlightens the physics of hierarchical phonon transport as approaching the Ioffe-Regel limit, and provides a numerical method that should be practically applicable to many materials with vibrational hierarchy.

en: Vibrational hierarchy leads to dual-phonon transport in low thermal conductivity crystals

dual-phonon-theory

display_name: dual-phonon-theory

theoretical-calculation

display_name: theoretical-calculation

thermal-conductivity

display_name: thermal-conductivity


en: Density functional theory calculations were used to obtain the generalized stacking fault energy curves in six BCC metals: Cr, Mo, Nb, Ta, V, and W. Among them, antiferromagnetism was considered only in Cr. Results based on non-magnetic Cr are denoted as Cr-NM.

en: Generalized stacking fault energy curves for six body-centered cubic refractory metals

body-centered-cubic-refractory-metals

display_name: body-centered-cubic-refractory-metals

density-functional-theory

display_name: density-functional-theory

generalized-stacking-fault-energies

display_name: generalized-stacking-fault-energies


en: In solution crystallization, solvent has a profound effect on controlling crystal morphology. However, the role played by solvents in affecting crystal morphology remains elusive. Here, we accompany experiments with molecular dynamics simulations to investigate crystallization of an anti-tuberculosis drug, isoniazid, in different solvents. Experiments show that isoniazid grows as needle-like crystals in water, while in alcohols such as methanol, ethanol and isopropanol, it exhibits a rod-like crystal habit. The aspect ratio of isoniazid crystals decreases with the decrease in the relative solvent polarity. We modeled these experiments by performing molecular dynamics simulations of isoniazid crystallization in different solvents at constant chemical potential thus keeping the solution concentration constant. The simulation results reveal a rough growth mechanism for the fast growing (1 1 0) surface, and bulk transport of the solute from solution to the growing surface is the limiting-step. In accordance with experiments, the relative growth rate of this surface decreases from methanol, ethanol to isopropanol. On the other hand, the slow growing (0 0 2) surface appears to follow a stepwise growth mechanism, with a surface integration step chiefly controlling the growth. The relative growth rate of this surface increases from methanol to ethanol and isopropanol.

en: Solvent-mediated morphology selection of the active pharmaceutical ingredient isoniazid: Experimental and simulation studies

crystal-growth

display_name: crystal-growth

marvel

display_name: marvel

morphology

display_name: morphology

solution-crystallization

display_name: solution-crystallization

solvent-effect-on-crystal-shape

display_name: solvent-effect-on-crystal-shape


en: Alchemistic simulations are versatile tools for prediction of relative free energy differences. Accuracy of these methods depends critically on sampling of orthogonal (non-Alchemistic) degrees of freedom. Here we apply flying Gaussian method to accelerate such orthogonal degree of freedom – peptide bond cis/trans iso-merisation.  The approach is demonstrated on prediction of pKa value of N-acetylproline. Isomerization of the amide bond was accelerated in this simulation by multiple orders of magnitude.  Alchemistic free energy was obtained by reweighting.  We also demonstrate that the accuracy of biased Alchemistic simulations can be significantly improved by a simple redefinition of the thermodynamic cycle using a flattening.  Such redefinition can be applied a posteriori to improve the accuracy of biased Alchemistic simulations.

en: Improving accuracy of biased Alchemistic simulations

alchemistic-simulations

display_name: alchemistic-simulations

biased-simulations

display_name: biased-simulations

reweighting

display_name: reweighting


en: This work combines a machine learning potential energy function with a modular enhanced sampling scheme to obtain statistically converged thermodynamical properties of flexible medium size organic molecules at high ab initio level. We offer a modular environment in the python package MORESIM that allows custom design of  replica exchange simulations with any level of theory including ML-based potentials. Our specific combination of Hamiltonian and reservoir replica exchange is shown to be a powerful technique to accelerate enhanced sampling simulations and explore free energy landscapes with a quantum chemical accuracy unattainable otherwise (e.g., DLPNO-CCSD(T)/CBS quality). This engine is used to demonstrate the relevance of accessing the ab initio free energy landscapes of molecules whose stability is determined by a subtle interplay between variations in the underlying potential energy and conformational entropy (i.e., a bridged asymmetrically polarized dithiacyclophane and a widely used organocatalyst) both in the gas phase and in solution (implicit solvent).

en: Hamiltonian-Reservoir Replica Exchange and Machine Learning Potentials for Computational Organic Chemistry

accelerated-sampling

display_name: accelerated-sampling

epfl

display_name: epfl

hamiltonian-replica-exchange

display_name: hamiltonian-replica-exchange

machine-learning

display_name: machine-learning


en: We present in full detail a newly developed formalism enabling density functional perturbation theory (DFPT) calculations from a DFT+U ground state. The implementation includes ultrasoft pseudopotentials and is valid for both insulating and metallic systems. It aims at fully exploiting the versatility of DFPT combined with the low-cost DFT+U functional. This allows to avoid computationally intensive frozen-phonon calculations when DFT+U is used to eliminate the residual electronic self-interaction from approximate functionals and to capture the localization of valence electrons e.g. on d or f states. In this way, the effects of electronic localization (possibly due to correlations) are consistently taken into account in the calculation of specific phonon modes, Born effective charges, dielectric tensors and in quantities requiring well converged sums over many phonon frequencies, as phonon density of states and free energies. The new computational tool is applied to two representative systems, namely CoO, a prototypical transition metal monoxide and LiCoO2, a material employed for the cathode of Li-ion batteries. The results show the effectiveness of our formalism to capture in a quantitatively reliable way the vibrational properties of systems with localized valence electrons.

en: Hubbard-corrected density functional perturbation theory with ultrasoft pseudopotentials

materialscloud

en:
Materials Cloud is a platform built to enable the seamless sharing and dissemination of resources in computational materials science, offering educational, research, and archiving tools; simulation software and services; and curated and raw data. These underpin published results and empower data-based discovery, compliant with data management plans and the FAIR principles.

In the Materials Cloud you can browse, explore, download, or deposit raw and curated data (in the Discover, Explore, and Archive sections); you can access cloud or redeployable simulation services (from AiiDAlab turnkey simulations to the Quantum Mobile virtual machine, the AiiDA registry of plugins and workflows, and the OSSCAR notebooks, in the Work section), and you can use all our educational material, tutorials and lectures (in the Learn section).

cscs

display_name: cscs

density-functional-perturbation-theory

display_name: density-functional-perturbation-theory

dfptu

display_name: dfptu

dftu

display_name: dftu

phonons

display_name: phonons

snsf

display_name: snsf

transition-metal-oxides

display_name: transition-metal-oxides


en:
Contradictory theoretical results for oxygen vacancies (VO) in SrTiO3 (STO) were often related to the peculiar properties of STO, which is a d0 transition metal oxide with mixed ionic-covalent bonding. Here, we apply, for the first time, density functional theory (DFT) within the extended Hubbard DFT+U+V approach, including on-site as well as inter-site electronic interactions, to study oxygen-deficient STO with Hubbard U and V parameters computed self-consistently (SC) via density-functional perturbation theory. Our results demonstrate that the extended Hubbard functional is a promising approach to study defects in materials with electronic properties similar to STO. Indeed, DFT+U+V provides a better description of stoichiometric STO compared to standard DFT or DFT+U, the band gap and crystal field splitting being in good agreement with experiments.
In turn, also the description of the electronic properties of oxygen vacancies in STO is improved, with formation energies in excellent agreement with experiments as well as results obtained with the most frequently used hybrid functionals, however at a fraction of the computational cost. While our results do not fully resolve the contradictory findings reported in literature, our systematic approach leads to a deeper understanding of their origin, which stems from different cell sizes, STO phases, the exchange-correlation functional, and the treatment of structural relaxations and spin-polarization.

en: Self-consistent DFT+U+V study of oxygen vacancies in SrTiO3

materialscloud

en: Materials Cloud

dftuv

display_name: dftuv

oxygen-vacancies

display_name: oxygen-vacancies

prace

display_name: prace


en: The band alignment and the chemical bonding at the β-Ga2O3/AlN and β-Ga2O3/GaN interfaces are studied through hybrid functional calculations. We construct realistic slab models with III-O (III=Al, Ga) bonds dominating the chemical bonding at both interfaces. The epitaxial relationships between β-Ga2O3 and wurtzite AlN and GaN determined from experiments are adopted in our slab models. These models satisfy electron counting rules and all the dangling bonds are saturated at the interfaces. β-Ga2O3 is found to form type II heterojunctions with both wurtzite AlN and GaN. For the interfaces with AlN and GaN substrates, the calculated valence band offsets are 0.74 and 0.90 eV, respectively. These are in good agreement with experimental values. The obtained band alignments are useful for designing optical and electronic devices based on β-Ga2O3 and group III nitrides.

en: Band alignment at β-Ga2O3/III-N (III=Al, Ga) interfaces through hybrid functional calculations

envi

en: Environment

band-alignment

display_name: band-alignment

gallium-oxide

display_name: gallium-oxide

hybrid-functional

display_name: hybrid-functional


en: Unbiased molecular dynamics simulation was used to simulate systems containing hevein (HEV32) domain and mono-, di- or trisaccharide of GlcNAc. Carbohydrate molecules were placed outside the binding site. Three of six simulations led to formation of a carbohydrate-protein complex. Trajectories are available without water and are sampled every 100 ps. This study is one of the first application of docking by dynamics concept on carbohydrate-protein interactions.

en: Atomistic simulation of carbohydrate-protein complex formation: Hevein-32 domain

carbohydrate-protein-interactions

display_name: carbohydrate-protein-interactions

docking-by-dynamics

display_name: docking-by-dynamics

molecular-dynamics-simulation

display_name: molecular-dynamics-simulation


en: In the quest for improved photo switches, azoheteroarenes have emerged as a potential alternative to azobenzene. However, to date the number and types of these species that have subjected to study is insufficient to provide an in-depth understanding of the photochemical effects brought about by different substituents. Here, we computationally screen the optical properties and thermal stabilities of 512 azoheteroarenes that consist of eight different N-containing heteroarenes combined with 64 substitution patterns. The most promising compounds are identified and their properties rationalized based on the nature of the azoheteroarene core and the location and type of substitution patterns.

en: Exploring chemical space in the search for improved Azoheteroarene-based photoswitches

azobenzene-derivatives

display_name: azobenzene-derivatives

computations

display_name: computations

photoswitches

display_name: photoswitches

td-dft

display_name: td-dft


en: Elemental gallium possesses several intriguing properties such as a low melting point, a density anomaly and an electronic structure in which covalent and metallic features coexist. In order to simulate this complex system, we construct an ab-initio quality interaction potential by training a neural network on a set of density functional theory calculations performed on configurations generated in multithermal-multibaric simulations. Here we show that the relative equilibrium between liquid gallium, alpha-Ga, beta-Ga, and Ga-II is well described. The resulting phase diagram is in agreement with the experimental findings. The local structure of liquid gallium and its nucleation into alpha-Ga and beta-Ga are studied. We find that the formation of metastable beta-Ga is kinetically favored over the thermodinamically stable alpha-Ga. Finally, we provide insight into the experimental observations of extreme undercooling of liquid Ga.

en: Ab-initio phase diagram and nucleation of gallium

enhanced-sampling

display_name: enhanced-sampling

erc

display_name: erc

gallium-nucleation

display_name: gallium-nucleation

metadynamics

display_name: metadynamics

multithermal-multibaric-simulation

display_name: multithermal-multibaric-simulation

neural-networks

display_name: neural-networks

phase-diagram

display_name: phase-diagram


en: Accurately describing intermolecular interactions within the framework of Kohn-Sham density functional theory (KS-DFT) has resulted in numerous benchmark databases over the past two decades. By far, the largest efforts have been spent on closed-shell, neutral dimers for which today, the interaction energies and geometries can be accurately reproduced by various combinations of dispersion-corrected density functional approximations (DFAs). In sharp contrast, charged, open-shell dimers remain a challenge as illustrated by the analysis of the OREL26rad benchmark set consisting of pi-dimer radical cations. Aside from the methodological aspect, achieving a proper description of radical cationic complexes is appealing due to their role as models for charge carriers in organic semiconductors. In the interest of providing an assessment of more realistic dimer systems, we construct a dataset of large radical cationic dimers (CryOrel) and jointly train the 19 parameters of a dispersion corrected, range-separated hybrid density functional (wB97X-dDsC), with the objective of providing the maximum balance between the treatment of long-range London dispersion and reduction of the delocalization error. These conditions are essential to obtain accurate energy profiles and binding energies of charged, open-shell dimers. Comparisons with the performance of the parent wB97X functional series and state-of-the-art wavefunction based methods are provided.

en: Balancing DFT Interaction Energies in Charged Dimers Precursors to Organic Semiconductors

delocalization-error

display_name: delocalization-error

density-functional-theory

display_name: density-functional-theory

epfl

display_name: epfl

london-dispersion-interactions

display_name: london-dispersion-interactions

organic-semiconductors

display_name: organic-semiconductors

radical-cation-dimers

display_name: radical-cation-dimers

snsf

display_name: snsf


en: Weyl semimetals are crystals in which electron bands cross at isolated points in momentum space. Associated with each crossing point (or Weyl node) is an integer topological invariant known as the Berry monopole charge. The discovery of new classes of Weyl materials is driving the search for novel properties that derive directly from the Berry charge. The circular photogalvanic effect (CPGE), whereby circular polarized light generates a current whose direction depends on the helicity of the absorbed photons, is a striking example of a macroscopic property that emerges from Weyl topology. Recently, it was predicted that the rate of current generation associated with optical transitions near a Weyl node is proportional to its monopole charge. In Weyl semimetals that retain mirror symmetry the current is strongly suppressed by contributions from energy equivalent nodes of opposite charge. However, when all mirror symmetries are broken, as in chiral Weyl systems, nodes with opposite topological charge are no longer degenerate, opening a window of photon energies where the CPGE derived from the topological band structure can emerge. In this work we report the photon-energy dependence of the CPGE in the chiral Weyl semimetal RhSi. The spectrum reveals a helicity-sensitive response in a low-energy window that closes at 0.65 eV, in quantitative agreement with the bandstucture recently predicted from DFT calculations.

en: Helicity-dependent photocurrents in the chiral Weyl semimetal RhSi

cpge

display_name: cpge

rhsi

display_name: rhsi

thz

display_name: thz

weyl

display_name: weyl


en: Two-dimensional boron structures, due to the diversity of properties, attract great attention because of their potential applications in nanoelectronic devices. A series of TiB_x (4≤x≤11) monolayers are efficiently constructed through our motif based method and theoretically investigated through high-throughput first-principles calculations. The configurations are generated based on motifs of boron triangular/quadrilateral fragments and multicoordinate titanium-centered boron molecular wheels. Besides priviously reported TiB4 which was discovered by global search method, we predict that high symmetry monolayers TiB7 (Cmmm) and TiB9 (P31m) which are octa-coordinate and nona-coordinate titanium boride are thermodynamic stable. The TiB7 monolayer is a BCS superconductor with the transition temperature Tc up to 8K. The motif based approach is proved to be efficient in searching stable structures with a prior knowledge so that the potentially stable transition metal monolayers can be quickly constructed by using basic cluster motifs. As an efficient way of discovering materials, the method is easily extended to predict other type of materials which have common characteristic pattern in the structure.

en: Motif based high-throughput structure prediction of superconducting monolayer titanium boride

materialscloud

en:
Materials Cloud is a platform built to enable the seamless sharing and dissemination of resources in computational materials science, offering educational, research, and archiving tools; simulation software and services; and curated and raw data. These underpin published results and empower data-based discovery, compliant with data management plans and the FAIR principles.

In the Materials Cloud you can browse, explore, download, or deposit raw and curated data (in the Discover, Explore, and Archive sections); you can access cloud or redeployable simulation services (from AiiDAlab turnkey simulations to the Quantum Mobile virtual machine, the AiiDA registry of plugins and workflows, and the OSSCAR notebooks, in the Work section), and you can use all our educational material, tutorials and lectures (in the Learn section).

high-throughput

display_name: high-throughput

superconductor

display_name: superconductor

titanium-boride

display_name: titanium-boride

two-dimensional-material

display_name: two-dimensional-material


en: Electron energy bands, which are studied to explain electronic and optical properties of crystalline solids, often exhibit degeneracies called band-structure nodes. Here, we introduce non-Abelian topological charges that characterize line nodes inside the momentum space of -symmetric crystalline metals with weak spin-orbit coupling. We show that these are quaternion charges, similar to those describing disclinations in biaxial nematics. Starting from two-band considerations, we develop the complete many-band description of nodes in the presence of and mirror symmetries, which allows us to investigate the topological stability of nodal chains in metals. The non-Abelian charges put strict constraints on the possible nodal line configurations. Our analysis goes beyond the standard approach to band topology and implies the existence of 1D topological phases not present in existing classifications.

en: Supplementary Data for "Non-Abelian band topology in noninteracting metals"

materialscloud

en: Materials Cloud

band-topology

display_name: band-topology

marvel

display_name: marvel

model-hamiltonian

display_name: model-hamiltonian

non-abelian

display_name: non-abelian

pt-symmetric-crystalline-metals

display_name: pt-symmetric-crystalline-metals

topological-materials

display_name: topological-materials

vasp

display_name: vasp

wanniertools

display_name: wanniertools

weak-spin-orbit-coupling

display_name: weak-spin-orbit-coupling


en: Metal-organic frameworks (MOFs) consist of metal nodes that are connected by organic linkers. They are thus highly chemically tunable materials given the broad range of potential linkers and nodes that can be chosen for their synthesis. Their tunability has recently sparked interest for the development of new MOF photo-catalysts for energy-related applications such as hydrogen (H2) evolution and CO2 reduction. The sheer amount of potentially synthesizable MOFs requires to define descriptors that allow to predict their performance with this aim. Herein we propose a systematic computational protocol to determine two energy-based descriptors that are directly related to the performance of a MOF as a photocatalyst. These descriptors assess the UV-vis light absorption capability and the band energy alignment with respect to redox processes and/or co-catalysts energy levels. High-throughput screening based on cost-effective computations of these features is envisioned to aid the discovery of new promising photoactive systems.

en: Energy-based Descriptors for Photo-Catalytically Active Metal-Organic Frameworks Discovery

envi

en: Environment

mof

display_name: mof

photocatalysis

display_name: photocatalysis

screening

display_name: screening


en: We propose a self-consistent site-dependent Hubbard U approach for density functional theory (DFT)+U calculations of defects in complex transition metal oxides, using Hubbard parameters computed via linear response theory. The formation of a defect locally perturbs the chemical environment of Hubbard sites in its vicinity, resulting in different Hubbard U parameters for different sites. Using oxygen vacancies in SrMnO3 as a model system, we investigate the dependence of U on the chemical environment and study its influence on the structural, electronic, and magnetic properties of defective bulk and strained thin-film structures. Our results show that a self-consistent U improves the description of stoichiometric bulk SrMnO3 with respect to generalized gradient approximation (GGA) or GGA+U calculations using an empirical U. For defective systems, U changes as a function of the distance of the Hubbard site from the defect, its oxidation state, and the magnetic phase of the bulk structure. Taking into account this dependence, in turn, affects the computed defect formation energies and the predicted strain- and/or defect-induced magnetic phase transitions, especially when occupied localized states appear in the band gap of the material upon defect creation.

en: Self-consistent site-dependent DFT+U study of stoichiometric and defective SrMnO3

defects

display_name: defects

electronic-properties--materials

display_name: electronic-properties--materials

self-consistent-site-dependent-dftu

display_name: self-consistent-site-dependent-dftu


en:
On‐surface synthesis is a unique tool for growing low‐dimensional carbon nanomaterials with precise structural control down to the atomic level.
One of the most applied reactions to covalently interlink molecular precursors is dehalogenative aryl‐aryl coupling.
Failures in this process are often related to the steric hindrance between reactants, which may arise due to their coplanarity upon adsorption on a surface. In a recent work we proposed a copolymerization approach to overcome the limitations that prevent intermolecular homocoupling. We used suitable linkers as additional reactants to demonstrate formation of fully conjugated polycyclic nanowires incorporating non‐benzenoid rings. This record contains data to support the experimental and theoretical evidences discussed in the manuscript.

en: Overcoming steric hindrance in aryl-aryl homocoupling via on-surface copolymerization

ab-initio

display_name: ab-initio

nanomaterials

display_name: nanomaterials

on-surface-synthesis

display_name: on-surface-synthesis

scanning-probe-microscopy

display_name: scanning-probe-microscopy


en: Finding heterogeneous catalysts that are superior to homogeneous ones for selective organic transformation is a major challenge in catalysis. Here we show how micropores in metal-organic frameworks (MOFs) push homogeneous catalytic reactions into kinetic regimes inaccessible under standard conditions. Such property allows branched selectivity up to 90% in the Co-catalysed hydroformylation of olefins without directing groups, not achievable with existing catalysts. This finding has a big potential in the production of aldehydes for the fine chemical industry. Monte Carlo and density functional theory simulations combined with kinetic models show that the micropores of MOFs with UMCM-1 and MOF-74 topologies increase the olefins density beyond neat conditions while partially preventing the adsorption of syngas leading to high branched selectivity. The easy experimental protocol and the chemical and structural flexibility of MOFs will attract the interest of the fine chemical industries towards the design of heterogeneous processes with exceptional selectivity.

en: Metal-organic frameworks as kinetic modulators for branched selectivity in hydroformylation

catalysis

display_name: catalysis

marvel

display_name: marvel

metal-organic-frameworks

display_name: metal-organic-frameworks


en:
This database contains computationally generated atomic structures of glass-ceramics lithium thiophosphates (gc-LPS) with the general composition (Li2S)x(P2S5)1-x in the XCrySDen structure format (XSF). Total energies and interatomic forces from density-functional theory (DFT) calculations are included as additional meta information. The extended XSF format is compatible with the atomic energy network (ænet) package for artificial neural network (ANN) potential construction and application. The DFT calculations used projector-augmented-wave (PAW) pseudopotentials and the Perdew−Burke−Ernzerhof (PBE) exchange-correlation functional as implemented in the Vienna Ab Initio Simulation Package (VASP) and a kinetic energy cutoff of 520 eV. The first Brillouin zone was sampled using VASP's fully automatic k-point scheme with a length parameter Rk = 25Å. The gc-LPS structures were generated using a combination of different sampling methods. Initial amorphous structure models were generated with ab initio molecular dynamics (AIMD) simulations of supercells at 1200 K using a Nose-Hoover thermostat with a time step of 1 fs. To obtain near-ground-state structures as reference for the machine-learning potential, 150 evenly spaced snapshots were extracted from the AIMD trajectories that were reoptimized with DFT geometry optimizations at zero Kelvin. Additional structures were generated by scaling the lattice parameters of the crystalline LPS structures (see below) by ±15% and perturbing atomic positions in AIMD simulations as described above.
The resulting database was used to train a specialized ANN potential for the sampling of structures along the Li2S–P2S5 composition line with a genetic-algorithm (GA) as implemented in the atomistic evolution (ævo) package, following a previously reported protocol. Starting from supercells of the ideal crystal structures, either Li and S atoms were removed with a ratio of 2:1, or P and S atoms were removed with a ratio of 2:5, and low-energy configurations were determined with GA sampling. A population size of 32 trials and a mutation rate of 10% were employed. The ANN potential was iteratively refined by including additional sampled structures in the training. For each composition, at least 10 lowest energy structure models identified with the ANN-GA approach were selected and fully relaxed with DFT.
Also included in the present database are the XSF files of the previously reported crystalline phases LiPS3, Li2PS3, Li4P2S7, Li7P3S11, α-Li3PS4, β-Li3PS4, γ-Li3PS4, and Li48P16S61. The crystal structures were obtained from the Inorganic Crystal Structure Database (ICSD), the Materials Project (MP) database, the Open Quantum Materials Database (OQMD), and the AFLOW database. The directory names indicate the journal reference and the database.
Further details can be found in the associated research article.

en: Structure database of glass-ceramic lithium thiophosphate electrolytes

aenet

display_name: aenet

dft

display_name: dft

lithium-thiophosphates

display_name: lithium-thiophosphates

solid-electrolytes

display_name: solid-electrolytes


en:
Frustrated Lewis pairs (FLPs), featuring reactive combinations of Lewis acids and Lewis bases, have been utilized for myriad metal-free homogeneous catalytic processes. Immobilizing the active Lewis sites to a solid support, especially to porous scaffolds, has shown great potential to ameliorate FLP catalysis by circumventing some of its inherent drawbacks, such as product separation and catalyst recyclability. Nevertheless, designing immobilized Lewis pair active sites (LPASs) is challenging due to the requirement of placing the donor and acceptor centers in appropriate geometric arrangements while maintaining the necessary chemical environment to perform catalysis, and clear design rules have not yet been established. In this work, we formulate simple guidelines to build highly active LPASs for direct catalytic hydrogenation of CO₂ through a large-scale screening of a diverse library of 25,000 immobilized FLPs.
The library is built by introducing boron-containing acidic sites in the vicinity of the existing basic nitrogen sites of the organic linkers of metal-organic frameworks collected in a "top-down" fashion from an experimental database. The chemical and geometrical appropriateness of these LPASs for CO₂ hydrogenation is determined by evaluating a series of simple descriptors representing the intrinsic strength (acidity and basicity) of the components and their spatial arrangement in the active sites. Analysis of the leading candidates enables the formulation of pragmatic and experimentally-relevant design principles and they constitute the starting point for further exploration of FLP-based catalysts for the reduction of CO₂.

en: Engineering  frustrated lewis pair active sites in porous organic scaffolds for catalytic CO₂ hydrogenation

epfl

display_name: epfl

frustrated-lewis-pairs

display_name: frustrated-lewis-pairs

molecular-catalysts

display_name: molecular-catalysts

volcano-plot

display_name: volcano-plot


en:
This Dataset contains Supplementary information to the article "Effects of perturbation order and basis set on alchemical predictions" by Giorgio Domenichini, Guido Falk von Rudorff and O. Anatole von Lilienfeld.
Our numerical analysis of potential energy estimates, and resulting binding curves, is based on CCSD reference results, and is limited to all neutral diatomics with 14 electrons (AlH ...  N2).
From those data can be predicted binding energy, equilibrium distance, and vibrational frequencies of neighboring out-of-sample diatomics with near CCSD quality using perturbations up to 5th order.

The data stored as Comma Separated Value files (.csv) contain all the predictions within the 14 electron diatomics series, those are referred to the sections IIIA-IIIE of the article.
To every file corresponds one of the eight basis sets used.
The data are stored using consistently atomic units: Bohrs for length, electrons for charge and Hartrees for energy.
For a better visualization using Jupyter notebooks and Pandas library the notebook "Display_data.ipynb" already contains the code to open the data as pandas' data frames.

en: Effects of perturbation order and basis set on alchemical predictions within 14 electron diatomic molecules series, detailed analysis of the various sources of errors

materialscloud

en:
Materials Cloud is a platform built to enable the seamless sharing and dissemination of resources in computational materials science, offering educational, research, and archiving tools; simulation software and services; and curated and raw data. These underpin published results and empower data-based discovery, compliant with data management plans and the FAIR principles.

In the Materials Cloud you can browse, explore, download, or deposit raw and curated data (in the Discover, Explore, and Archive sections); you can access cloud or redeployable simulation services (from AiiDAlab turnkey simulations to the Quantum Mobile virtual machine, the AiiDA registry of plugins and workflows, and the OSSCAR notebooks, in the Work section), and you can use all our educational material, tutorials and lectures (in the Learn section).

apdft

display_name: apdft

erc

display_name: erc

error-estimation

display_name: error-estimation

quantum-alchemy

display_name: quantum-alchemy

snsf

display_name: snsf


quantum-espresso-at-the-exascale

en: Quantum ESPRESSO is an open-source distribution of computer codes for quantum-mechanical materials modeling, based on density-functional theory, pseudo-potentials, and plane waves, and renowned for its performance on a wide range of hardware architectures, from laptops to massively parallel computers, as well as for the breadth of its applications. In this paper we present a motivation and brief review of the ongoing effort to port Quantum ESPRESSO onto heterogeneous architectures based on hardware accelerators, which will overcome the energy constraints that are currently hindering the way towards exascale computing.

en: Quantum ESPRESSO at the exascale

materialscloud

en: Materials Cloud

title_for_slug: quantum-espresso-at-the-exascale

density-functional-theory

display_name: density-functional-theory

first-principles

display_name: first-principles

gpu

display_name: gpu

hpc

display_name: hpc

max

display_name: max

nccr

display_name: nccr


en: Reducing and/or utilizing CO2 in the atmosphere is mandatory to decrease its negative effects as greenhouse gas. The reverse water gas shift reaction (rWGS) is one of the most promising routes for CO2 valorization. Here, we show that Ni/La-doped ceria catalysts, prepared by the solution combustion synthesis method, has an excellent catalytic performance per unit mass of catalyst. Structure-activity correlations obtained using a combination of different techniques such as X-ray and neutron diffraction, Raman spectroscopy, in-situ NAP-XPS, Electron Microscopy, and catalytic testing, point out to optimum values for the Ni loading and the La proportion. Density functional theory calculations of the elementary steps of the reaction on model Ni/ceria catalysts aid toward the microscopic understanding of the active sites nature. Metallic Ni activates H2 dissociation and a certain La doping maximizes Ce3+ sites, which supplies greater available oxygen to form H2O. These findings are essential for the rational design of highly efficient and selective rWGS catalysts.

en: Elucidating structure and function of Ni/La-doped-ceria catalysts for CO2 reduction by the reverse water gas shift reaction

envi

en: Environment

lanthanum

display_name: lanthanum

nickel

display_name: nickel

oxygen-vacancies

display_name: oxygen-vacancies

rwgs

display_name: rwgs


en: The lighting of the future is expected to be light weight, flexible, highly efficient, non-expensive and fabricated in an environmentally friendly way. Organic light emitting diodes meet all these requirements and can be fabricated using inexpensive and roll-to-roll compatible printing techniques. They however often use low work function, highly reactive metals, such as barium and calcium to facilitate electron injection, deposited using expensive and non-continuous vacuum techniques. Efficient and stable alternatives can be found in the aliphatic amines, polyethylenimine and polyethylenimine(ethoxylated), which shift the work function of aluminum favorably for electron injection. This work demonstrates ultrasonic spray coating of polyethylenimine and polyethylenimine(ethoxylated) as electron injection and transport layer for OLEDs, reducing the work function of the aluminum cathode by 0.355 eV allowing a luminous efficacy comparable to that of the OLEDs using calcium/aluminum electrodes. Slightly higher luminous results are noted for the OLEDs with spin coated PEIE, indicating that the surface morphology and thickness of the polyethylenimine(ethoxylated) layer are crucial factors: ultrasonic spray coated polyethylenimine(ethoxylated) layers have an increased overall thickness and surface roughness. This study confirms the versatility of ultrasonic spray coating and the suitability of polyethylenimine(ethoxylated) as excellent electron injection and transport layer for OLEDs and paves the way towards fully spray coated OLEDs. The produced OLEDs were measured using a Keithley 2401 source meter (Keithley Instruments, Cleveland, Ohio, USA) to obtain the current and voltage characteristics and by using an absolute calibrated integrating sphere spectrometer from Avantes (Apeldoorn, The Netherlands) to acquire the luminous flux. The luminous efficacy was then calculated by dividing the luminous flux by the used electrical power. This data is presented here.

en: Ultrasonic spray coating of polyethylenimine (ethoxylated) as electron injection and transport layer for organic light emitting diodes

electron-injection-and-transport-layer

display_name: electron-injection-and-transport-layer

experimental

display_name: experimental

organic-light-emitting-diodes

display_name: organic-light-emitting-diodes

polyethylenimine-ethoxylated

display_name: polyethylenimine-ethoxylated

printing-technique

display_name: printing-technique

ultrasonic-spray-coating

display_name: ultrasonic-spray-coating


en:
Rozenite (FeSO₄·4H₂O) is a candidate mineral component of the polyhydrated sulfate deposits on the surface and in the subsurface of Mars. In order to better understand its behavior at temperature conditions prevailing on the martian surface and aid its identification in ongoing and future Rover missions we have carried out a combined experimental and computational study of the mineral's structure and properties. We collected neutron powder diffraction data at temperatures ranging from 21 – 290 K, room temperature synchrotron X-ray data and Raman spectra. Moreover, first-principles calculations of the vibrational properties of rozenite were carried out to aid the interpretation of the Raman spectrum.  In this work, we demonstrated how combining Raman spectroscopy and X-ray diffraction of the same sample material sealed inside a capillary with complementary first principles calculations yields accurate reference Raman spectra. This workflow enables the construction of a reliable Raman spectroscopic database for planetary exploration, which will be invaluable to shed light on the geological past as well as in identifying resources for the future colonization of planetary bodies throughout the solar system.
In this dataset, the self-consistent DFT+U as well as Γ-point phonon calculations, that were compared to the experimentally determined frequencies of the Raman-active modes, are reported, whereas the experimental data was submitted to crystallographic data-bases (i.e., CCSD and ICSD).

en: Low-temperature crystallography and vibrational properties of rozenite (FeSO₄·4H₂O), a candidate mineral component of the polyhydrated sulfate deposits on Mars

dftu

display_name: dftu

infrared

display_name: infrared

mars

display_name: mars

phonons

display_name: phonons

raman

display_name: raman

spectroscopy

display_name: spectroscopy


en:
When complex mechanisms are involved, pinpointing high-performance materials within large databases is a major challenge in materials discovery. We focus here on phonon-limited conductivities, and study 2D semiconductors doped by field effects. Using state-of-the-art density-functional perturbation theory and Boltzmann transport equation, we discuss 11 monolayers with outstanding transport properties.
These materials are selected from a computational database of exfoliable materials providing monolayers that are dynamically stable and that do not have more than 6 atoms per unit cell. We first analyze electron-phonon scattering in two well-known systems: electron-doped InSe and hole-doped phosphorene. Both are single-valley systems with weak electron-phonon interactions, but they represent two distinct pathways to fast transport: a steep and deep isotropic valley for the former and strongly anisotropic electron-phonon physics for the latter.
We identify similar features in the database and compute the conductivities of the relevant monolayers. This process yields several high-conductivity materials, some of them only very recently emerging in the literature (GaSe, Bi₂SeTe₂, Bi₂Se₃, Sb₂SeTe₂), others never discussed in this context (AlLiTe₂, BiClTe, ClGaTe, AuI). Comparing these 11 monolayers in detail, we discuss how the strength and angular dependency of the electron-phonon scattering drives key differences in the transport performance of materials despite similar valley structure. We also discuss the high conductivity of hole-doped WSe₂, and how this case study shows the limitations of a selection process that would be based on band properties alone.
In this entry we provide the AiiDA database with the calculations of phonons and electron-phonon interactions for the 11 materials, along with the python library to collect and visualise the data, solve the Botzmann transport equation, and launch the same workflows for other 2D materials. To guide the reader, we include a Jupyter notebook showing how to extract the data, use the basic functionalities of the library, and regenerate the plots included in the associated paper.

en: Profiling novel high-conductivity 2D semiconductors

electron-phonon-coupling

display_name: electron-phonon-coupling

prace

display_name: prace

snsf

display_name: snsf

transport

display_name: transport


en: Application of the nonadiabatic molecular dynamics (NAMD) approach is severely limited to studying carrier dynamics in the momentum space, since a supercell is required to sample the phonon excitation and electron-phonon (e-ph) interaction at different momenta in a molecular dynamics simulation. Here, we develop an ab initio approach for the real-time quantum dynamics for charge carriers in the momentum space (NAMD_k) by directly introducing the e-ph coupling into the Hamiltonian based on the harmonic approximation. The NAMD_k approach maintains the quantum zero-point energy and proper phonon dispersion, and includes memory effects of phonon excitation. The application of NAMD_k to the hot carrier dynamics in graphene reveals the phonon-specific relaxation mechanism. An energy threshold of 0.2eV, defined by two optical phonon modes strongly coupled to the electrons, separates the hot electron relaxation into fast and slow regions with the lifetimes of pico- and nano-seconds, respectively. The NAMD_k approach provides a powerful tool to understand real-time carrier dynamics in the momentum space for different materials.

en: Ab initio real-time quantum dynamics of charge carriers in momentum space

first-principles

display_name: first-principles

nonadiabatic-molecular-dynamics

display_name: nonadiabatic-molecular-dynamics


en:
Symmetry is one of the most central concepts in physics, and it is no surprise that it has also been widely adopted as an inductive bias for machine-learning models applied to the physical sciences. This is especially true for models targeting the properties of matter at the atomic scale. Both established and state-of-the-art approaches, with almost no exceptions, are built to be exactly equivariant to translations, permutations, and rotations of the atoms. Incorporating symmetries—rotations in particular—constrains the model design space and implies more complicated architectures that are often also computationally demanding. There are indications that unconstrained models can easily learn symmetries from data, and that doing so can even be beneficial for the accuracy of the model. We demonstrate that an unconstrained architecture can be trained to achieve a high degree of rotational invariance, testing the impacts of the small symmetry breaking in realistic scenarios involving simulations of gas-phase, liquid, and solid water. We focus specifically on physical observables that are likely to be affected—directly or indirectly—by non-invariant behavior under rotations, finding negligible consequences when the model is used in an interpolative, bulk, regime. Even for extrapolative gas-phase predictions, the model remains very stable, even though symmetry artifacts are noticeable. We also discuss strategies that can be used to systematically reduce the magnitude of symmetry breaking when it occurs, and assess their impact on the convergence of observables.

This archive collect the input files, scripts, and data for the paper referenced below. In particular, it contains the trained MLIP for this work, the input files for simulations, the post-processing scripts and their outputs, as well as the plotting scripts and resulting figures. A detailed readme can be found below, and a more detailed one in each subfolder.

The data in this archive is mirrored at https://github.com/sirmarcel/eqt-archive, where issues can be raised and discussed.

en: Probing the effects of broken symmetries in machine learning

equivariance

display_name: equivariance

machine-learning

display_name: machine-learning

water

display_name: water


en: We present an efficient procedure for constructing nonempirical hybrid functionals to accurately predict band gaps of extended systems. We determine mixing parameters by enforcing the generalized Koopmans' condition on localized electron states, which are achieved by inserting an optimized potential probe. Application of this scheme to a large set of materials yields band gaps with a mean error of 0.30 eV with respect to experiment. Next, we consider a perturbative one-shot approach in which the single- particle eigenvalues are calculated with the wave functions obtained at the semilocal level. In this way, the computational cost is reduced by ∼85% without loss of accuracy. The scheme is found to be robust upon consideration of different defect species and functional forms.

en: One-shot approach for enforcing piecewise linearity on hybrid functionals: application to band-gap predictions

materialscloud

en:
Materials Cloud is a platform built to enable the seamless sharing and dissemination of resources in computational materials science, offering educational, research, and archiving tools; simulation software and services; and curated and raw data. These underpin published results and empower data-based discovery, compliant with data management plans and the FAIR principles.

In the Materials Cloud you can browse, explore, download, or deposit raw and curated data (in the Discover, Explore, and Archive sections); you can access cloud or redeployable simulation services (from AiiDAlab turnkey simulations to the Quantum Mobile virtual machine, the AiiDA registry of plugins and workflows, and the OSSCAR notebooks, in the Work section), and you can use all our educational material, tutorials and lectures (in the Learn section).

density-functional-theory

display_name: density-functional-theory

pseudopotentials

display_name: pseudopotentials

quantum-espresso

display_name: quantum-espresso


en: The nature of order in low-temperature phases of some materials is not directly seen by experiment. Such "hidden orders" (HO) may inspire decades of research to identify the mechanism underlying those exotic states of matter. In insulators, HO phases originate in degenerate many-electron states on localized f or d shells that may harbor high-rank multipole moments. Coupled by inter-site exchange, those moments form a vast space of competing order parameters. Here, we show how the ground state order and magnetic excitations of a prototypical HO system, neptunium dioxide NpO2, can be fully described by a low-energy Hamiltonian derived by a many-body ab initio force theorem method. Superexchange interactions between the lowest crystal-field quadruplet of Np4+ ions induce a primary non-collinear order of time-odd rank-5 (triakontadipolar) moments with a secondary quadrupole order preserving the cubic symmetry of NpO2. Our study also reveals an unconventional multipolar exchange-striction mechanism behind the anomalous volume contraction of the NpO2 HO phase.

en: Hidden order and multipolar exchange striction in a correlated f-electron system

materialscloud

en: Materials Cloud

ab-initio

display_name: ab-initio

effective-hamiltonians

display_name: effective-hamiltonians

erc

display_name: erc

hidden-order

display_name: hidden-order

linear-response

display_name: linear-response

strongly-correlated-electrons

display_name: strongly-correlated-electrons


en:
Thouless' quantization of adiabatic particle transport permits to associate an integer topological charge with each atom of an electronically gapped material. If these charges are additive and independent of atomic positions, they provide a rigorous definition of atomic oxidation states and atoms can be identified as integer-charge carriers in ionic conductors. Whenever these conditions are met, charge transport is necessarily convective, i.e. it cannot occur without substantial ionic flow, a transport regime that we dub trivial. We show that the topological requirements that allow these conditions to be broken are the same that would determine a Thouless' pump mechanism if the system were subject to a suitably defined time-periodic Hamiltonian. The occurrence of these requirements determines a non-trivial transport regime whereby charge can flow without any ionic convection, even in electronic insulators.
These results are first demonstrated with a couple of simple molecular models that display a quantum pump mechanism upon introduction of a fictitious time dependence of the atomic positions along a closed loop in configuration space. We finally examine the impact of our findings on the transport properties of non-stoichiometric alkali-halide melts, where the same topological conditions that would induce a quantum pump mechanism along certain closed loops in configuration space also determine a non-trivial transport regime such that most of the total charge current results to be uncorrelated from the ionic ones.
In this record we collect the time series of the electric currents, displaced dipoles, and energy band gaps supporting the plots and relevant results supporting our findings.

en: Oxidation states, Thouless' pumps, and nontrivial ionic transport in nonstoichiometric electrolytes

envi

en: Environment

charge-transport

display_name: charge-transport

max

display_name: max

solvation

display_name: solvation

thouless-pump

display_name: thouless-pump

transport-properties

display_name: transport-properties


en: Molecular dynamics is a versatile and powerful method to study diffusion in solid-state ionic conductors, requiring minimal prior knowledge of equilibrium or transition states of the system's free energy surface. However, the analysis of trajectories for relevant but rare events, such as a jump of the diffusing mobile ion, is still rather cumbersome, requiring prior knowledge of the diffusive process in order to get meaningful results. In this work we present a novel approach to detect the relevant events in a diffusive system without assuming prior information regarding the underlying process. We start from a projection of the atomic coordinates into a landmark basis to identify the dominant features in a mobile ion's environment. Subsequent clustering in landmark space enables a discretization of any trajectory into a sequence of distinct states. As a final step, the use of the Smooth Overlap of Atomic Positions descriptor allows distinguishing between different environments in a straightforward way. We apply this algorithm to ten Li-ionic systems and conduct in-depth analyses of cubic Li7La3Zr2O12, tetragonal Li10GeP2S12, and the β-eucryptite LiAlSiO4. We compare our results to existing methods, underscoring strong points, weaknesses, and insights into the diffusive behavior of the ionic conduction in the materials investigated.

en: Unsupervised landmark analysis for jump detection in molecular dynamics simulations

big-map

display_name: big-map

molecular-dynamics

display_name: molecular-dynamics

site-analysis

display_name: site-analysis

tracer-diffusion

display_name: tracer-diffusion


en:
The zinc–antimony phase space has been heavily investigated due to the structural complexity and abundance of high-performing thermoelectric materials. Consequentially, the desire to use zinc and antimony as framework elements to encage rattling cations and achieve phonon-glass-electron-crystal-type properties has remained an enticing goal with only two alkali metal clathrates to date, Cs₈Zn₁₈Sb₂₈ and K₅₈Zn₁₂₂Sb₂₀₇. Guided by Zintl electron-counting predictions, we explored the Ba–Zn–Pn (Pn = As, Sb) phase space proximal to the expected composition of the type-I clathrate. In situ powder X-ray diffraction studies revealed two "hidden" compounds which can only be synthesized in a narrow temperature range. The ex situ synthesis and crystal growth unveiled that instead of type-I clathrates, compositionally close but structurally different new clathrate-like compounds formed, Ba₂Zn₅As₆ and Ba₂Zn₅Sb₆. These materials crystallize in a unique structure, in the orthorhombic space group Pmna with the Wyckoff sequence i²h⁶gfe. Single-phase synthesis enabled the exploration of their transport properties. Rattling of the Ba cations in oversized cages manifested low thermal conductivity, which, coupled with the high Seebeck coefficients observed, are prerequisites for a promising thermoelectric material. Potential for further optimization of the thermoelectric performance by aliovalent doping was computationally analyzed.
Data is provided from both experiment and theory:
- CIF files containing the experimentally determined crystal structure for each compound.
- Quantum ESPRESSO input- and output-files for SCF, density of states, and bands calculations
- Boltztrap2 configuration file and output, containing electronic transport calculations
- LOBSTER configuration file and crystal orbital Hamilton population (COHP) outputs

en: New trick for an old dog: from prediction to properties of "hidden clathrates" Ba₂Zn₅As₆ and Ba₂Zn₅Sb₆

clathrate

display_name: clathrate

crystal-structure

display_name: crystal-structure

electrical-conductivity

display_name: electrical-conductivity

solvates

display_name: solvates

thermal-conductivity

display_name: thermal-conductivity

thermoelectric

display_name: thermoelectric


en:
Low-dimensional materials can display enhanced electronic, magnetic, and quantum properties. However, 1D exfoliable nanowires have not been explored as much as their 2D and 0D counterparts. To address this, we use the topological scaling algorithm to identify all sufficiently metastable materials in the Materials Project database which have bulk crystals with one-dimensional (1D) structural motifs. We narrow our search to 263 bulk precursors which exfoliate unique 1D nanowires and contain d-orbital valence electrons. After exfoliating nanowires from these bulk precursors and applying structural optimization, we determine thermodynamic stability in both exfoliation energy (per-atom) and line tension (per-Angstrom) units, the latter of which we argue is a better predictor of stability in 1D materials. We further calculate the ferromagnetic ordering of these isolated nanowire materials.

This repository reports the final atomic structure, thermodynamic stability, magnetic moment (assumed ferromagnetic), and MaterialsProject ID of the bulk precursor for the 1D nanowire materials found in this search. It further reports a list of MaterialsProject ID's for crystals which qualify as "bipartides", crystals which are actually two interwoven sub-networks within a single unit cell.

en: Stability and magnetic behavior of exfoliable nanowire 1D materials

dft

display_name: dft

high-throughput

display_name: high-throughput

nanowire

display_name: nanowire


en: Surface-catalyzed reactions have been used to synthesize carbon nanomaterials with atomically pre-defined structures. The recent discovery of a gold surface-catalyzed [3+3] cycloaromatization of isopropyl substituted arenes has enabled the on-surface synthesis of arylene-phenylene copolymers, where the surface activates the isopropyl substituents to form phenylene rings by intermolecular coupling. However, the resulting polymers suffered from undesired cross-linking when more than two molecules reacted at a single site. In the manuscript in which this data is discussed we show that such cross-links can be prevented through steric protection by attaching the isopropyl groups to larger arene cores. Upon thermal activation of isopropyl-substituted 8,9-dioxa-8a-borabenzo[fg]tetracene on Au(111), cycloaromatization is observed to occur exclusively between two molecules. The cycloaromatization intermediate formed by the covalent linking of two molecules is prevented from reacting with further molecules by the wide benzotetracene core, resulting in highly selective one-to-one coupling. Our findings extend the versatility of the [3+3] cycloaromatization of isopropyl substituents and point toward steric protection as a powerful concept for suppressing competing reaction pathways in on-surface synthesis.

en: Sterically selective [3+3] cycloaromatization in the on-surface synthesis of nanographenes

density-functional-theory

display_name: density-functional-theory

nc-afm

display_name: nc-afm

on-surface-synthesis

display_name: on-surface-synthesis

snsf

display_name: snsf

stm

display_name: stm


en: Cu2O has appealing properties as an electrode for photo-electrochemical water splitting, yet its practical performance is severely limited by inefficient charge extraction at the interface. Using hybrid DFT calculations, we investigate carrier capture processes by oxygen vacancies (VO) in the experimentally observed (√3×√3)R30° reconstruction of the dominant (111) surface. Our results show that these VO are doubly ionized and that associated defects states strongly suppress electron transport. In particular, the excited electronic state of a singly charged VO plays a crucial role in the non-radiative electron capture process with a capture coefficient of about 10^-9 cm3/s and a lifetime of 0.04 ps, explaining the experimentally observed ultrafast carrier relaxation. These results highlight that engineering the surface VO chemistry will be a crucial step in optimizing Cu2O for photoelectrode applications.

en: Importance of surface oxygen vacancies for ultrafast hot carrier relaxation and transport in Cu2O

carrier-capture

display_name: carrier-capture

cscs

display_name: cscs

hybrid-dft

display_name: hybrid-dft

oxygen-vacancies

display_name: oxygen-vacancies

surface-reconstruction

display_name: surface-reconstruction


en: Recently, ultrathin metal-oxide thin film transistors (TFTs) have shown very high on-off ratio and ultra sharp subthreshold swing, making them promising candidates for applications beyond conventional large-area electronics. While the on-off operation in typical TFTs results primarily from the modulation of charge carrier density by gate voltage, the high on-off ratio in ultrathin oxide TFTs can be associated with a large carrier mobility modulation, whose origin remains unknown. We investigate 3.5 nm-thick titanium oxide based ultrathin TFTs exhibiting 6-decade on-off ratio, predominantly driven by gate induced mobility modulation. The power law behavior of the mobility features two regimes, with a very high exponent at low gate voltages, unprecedented for oxide TFTs. We find that this phenomenon is well explained by the presence of high-density tail states near the conduction band edge, which supports carrier transport via variable range hopping. The observed two-exponent regimes reflect the bi-exponential distribution of the density of band-tail states. This improved understanding would be significant in fabricating high-performance ultrathin oxide devices.

en: Large mobility modulation in ultrathin amorphous titanium oxide transistors

materialscloud

en:
Materials Cloud is a platform built to enable the seamless sharing and dissemination of resources in computational materials science, offering educational, research, and archiving tools; simulation software and services; and curated and raw data. These underpin published results and empower data-based discovery, compliant with data management plans and the FAIR principles.

In the Materials Cloud you can browse, explore, download, or deposit raw and curated data (in the Discover, Explore, and Archive sections); you can access cloud or redeployable simulation services (from AiiDAlab turnkey simulations to the Quantum Mobile virtual machine, the AiiDA registry of plugins and workflows, and the OSSCAR notebooks, in the Work section), and you can use all our educational material, tutorials and lectures (in the Learn section).

amorphous-semiconductor

display_name: amorphous-semiconductor

field-effect-transistor

display_name: field-effect-transistor

mobility-modulation

display_name: mobility-modulation

titanium-oxide

display_name: titanium-oxide

variable-range-hopping

display_name: variable-range-hopping


en: Transitioning from small-scale to big-data studies has the potential to reveal new layers of intricacy that better facilitate and rationalize catalytic behavior. Given the computational resources available today, data-driven approaches can propel the next leap forward in catalyst design. Using a data-driven inspired workflow consisting of data generation, statistical analysis, and dimensionality reduction algorithms we explore trends surrounding the thermodynamics of a model hydroformylation reaction catalyzed by group 9 metals bearing phosphine ligands. Specifically, we introduce a type of "augmented" volcano plot, the energetic profile similarity (EPSim) map, as a means to easily visualize the similarity of each catalyst's complete catalytic cycle energy profile to that of a hypothetical ideal reference profile without relying upon linear scaling relationships. In addition to quickly identifying catalysts that most closely match the ideal thermodynamic catalytic cycle energy profile, these maps also enable a more refined comparison of species lying closely in standard volcano plots. For the reaction studied here, they inherently uncover the presence of multiple sets of scaling relationships differentiated by metal type, where iridium catalysts follow distinct relationships than cobalt/rhodium catalysts and have profiles that more closely match the ideal thermodynamic profile. Reconstituted molecular volcano plots confirm the findings of the EPSim maps by showing that hydroformylation thermodynamics are governed by two distinct volcano shapes, one for iridium catalysts and a second for cobalt/rhodium species.

en: Data-powered augmented volcano plots for homogeneous catalysis

materialscloud

en: Materials Cloud

augmented-volcano-plots

display_name: augmented-volcano-plots

big-data

display_name: big-data

epfl

display_name: epfl

epsim-maps

display_name: epsim-maps

homogeneous-catalysis

display_name: homogeneous-catalysis

hydroformilation

display_name: hydroformilation


en: In ceria-based catalysis, the shape of the catalyst particle, which determines the exposed crystal facets, profoundly affects its reactivity. The vibrational frequency of adsorbed carbon monoxide (CO) can be used as a sensitive probe to identify the exposed surface facets, provided reference data on well-defined single crystal surfaces together with a definitive theoretical assignment exist. We investigate the adsorption of CO on the CeO2 (110) and (111) surfaces and show that the commonly applied DFT(PBE)+U method does not provide reliable CO vibrational frequencies by comparing with state-of-the-art infrared spectroscopy experiments for monocrystalline CeO2 surfaces. Good agreement requires the hybrid DFT approach with the HSE06 functional. The failure of conventional DFT is explained in terms of its inability to accurately describe the facet- and configuration-specific donation and backdonation effects that control the changes in the C-O bond length upon CO adsorption and the CO force constant. Our findings thus provide a theoretical basis for the detailed interpretation of experiments and open up the path to characterize more complex scenarios, including oxygen vacancies and metal adatoms.

en: Vibrational frequencies of cerium oxide-bound CO: a challenge for conventional DFT methods

envi

en: Environment

comparison-between-several-functionals

display_name: comparison-between-several-functionals

donation-and-backdonation-effects

display_name: donation-and-backdonation-effects


en: We introduce OSCAR, a repository of thousands of experimentally derived (OSCAR seed and CSD-extracted) and combinatorially enriched organocatalysts (OSCAR!(NHC) and OSCAR!(DHBD) for N-heterocyclic carbenes and hydrogen bond donors, respectively). The  structures and corresponding stereoelectronic properties are publicly available and constitute the starting point to build generative and predictive models for organocatalyst performance.

en: OSCAR: An extensive repository of chemically and functionally diverse organocatalysts

carbenes

display_name: carbenes

catalysis

display_name: catalysis

electronic-structure

display_name: electronic-structure

nccr-catalysis

display_name: nccr-catalysis

organic-molecules

display_name: organic-molecules

organocatalysis

display_name: organocatalysis


en: Quasiharmonic theory of atomic vibrations usually fails to describe materials that undergo structural phase transitions, which is the case with germanium telluride (GeTe) at high temperatures. To correctly model vibrational properties of GeTe at high temperatures, we use the temperature dependent effective potential (TDEP) method (Physical Review B 88, 144301 (2013)). Collecting data needed to fit TDEP models involves running ab-initio molecular dynamics (MD) simulations. These MD simulations can be very CPU time consuming. In order to speed up MD simulations, we fitted an interatomic potential using the Gaussian Approximation Potential (GAP) approach (Physical Review Letters 104, 136403 (2010)) to obtain interatomic forces during MD simulations. This dataset consists of the training set of density functional theory energies and forces of GeTe for GAP, and the training script used to generate the interatomic potential.

en: Gaussian approximation potentials (GAP) for germanium telluride

gaussian-approximation-potential

display_name: gaussian-approximation-potential

germanium-telluride

display_name: germanium-telluride

interatomic-potential

display_name: interatomic-potential


en: We address the long-standing problem of the ground state of 1T-TaS₂ by computing the correlated electronic structure of stacked bilayers using the GW+EDMFT method. Depending on the surface termination, the semi-infinite uncorrelated system is either band insulating or exhibits a metallic surface state. For realistic values of the on-site and inter-site interactions, a Mott gap opens in the surface state, but it is smaller than the gap originating from the bilayer structure. Our results are consistent with recent scanning tunneling spectroscopy measurements for different terminating layers, and with our own photoemission measurements, which indicate the coexistence of spatial regions with different gaps in the electronic spectrum. By comparison to exact diagonalization data, we clarify the interplay between Mott insulating and band insulating behavior in this archetypal layered system.

en: Mott versus hybridization gap in the low-temperature phase of 1T-TaS₂

dmft

display_name: dmft

first-principles

display_name: first-principles

transition-metal-dichalcogenides

display_name: transition-metal-dichalcogenides