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

marvel

display_name: marvel

nanomaterials

display_name: nanomaterials

on-surface-synthesis

display_name: on-surface-synthesis


$oid: OBSOLETE

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

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

catalysis

display_name: catalysis

metal-organic-frameworks

display_name: metal-organic-frameworks

mof

display_name: mof


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

vasp

display_name: vasp


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

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

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

marvel

display_name: marvel

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

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: The energy level alignment across solvated molecule/semiconductor interfaces is a crucial property for the correct functioning of dye-sensitized photo-electrodes, where, following the absorption of solar light, a cascade of interfacial hole/electron transfer processes has to efficiently take place. In light of the difficulty of performing X-ray photoelectron spectroscopy measurements at the molecule/solvent/metal-oxide interface, being able to accurately predict the level alignment by first-principles calculations on realistic structural models would represent an important step toward the optimization of the device. In this respect dye/NiO surfaces, employed in p-type dye-sensitized solar cells, are undoubtedly challenging for ab initio methods and, also for this reason, much less investigated than the n-type dye/TiO2 counterpart. Here we consider the C343-sensitized NiO surface in water and combine ab initio Molecular Dynamics (AIMD) simulations with GW (G0W0) calculations, performed along the MD trajectory, to reliably describe the structure and energetics of the interface when explicit solvation and finite temperature effects are accounted for. We show that the differential perturbative correction on the NiO and molecule states obtained at GW level is mandatory to recover the correct (physical) interfacial energetics, allowing hole transfer from the semiconductor valence band to the HOMO of the dye. Moreover, the calculated average driving force quantitatively agrees with the experimental estimate.

en: Structure and energetics of dye-sensitized NiO interfaces in water from ab-initio MD and large-scale GW calculations

ab-initio

display_name: ab-initio

energy-level-alignment

display_name: energy-level-alignment

gw

display_name: gw

molecular-dynamics-simulation

display_name: molecular-dynamics-simulation

nio

display_name: nio

p-type-dssc

display_name: p-type-dssc


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

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).

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

materialscloud

en: Materials Cloud

envi

en: Environment

electron-phonon-coupling

display_name: electron-phonon-coupling

prace

display_name: prace

snsf

display_name: snsf

transport

display_name: transport


en: It has been well established that nitrogen coordinated transition metal, TM-N4-C (TM=Fe and Co) moieties, are responsible for the higher catalytic activity for the electrochemical oxygen reduction reaction. However, the results obtained using density functional theory calculations vary from one to another, which can lead to controversy. Herein, we assess the accuracy of the theoretical approach using different class of exchange-correlation functionals, i.e., Perdew-Burke-Ernzerhof (PBE) and revised PBE (RPBE), those with the Grimme's semiempirical dispersion correction (PBE+D3 and RPBE+D3), and the Bayesian error estimate functional with the nonlocal correlation (BEEF-vdW) on the reaction energies of oxygen reduction reaction on TM-N4 moieties in graphene and those with OH-termination. We found that the predicted overpotentials using RPBE+D3 are comparable and consistent with those using BEEF-vdW. Our finding indicates that a proper choice of the exchange-correlation functional is crucial to a precise description of the catalytic activity of this system.

en: Comparative density functional theory study for predicting oxygen reduction activity of single-atom catalyst

density-functional-theory

display_name: density-functional-theory

exchange-correlation-functional

display_name: exchange-correlation-functional

oxygen-reduction-reaction

display_name: oxygen-reduction-reaction

single-atom-catalyst

display_name: single-atom-catalyst


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: Machine learning potentials have become an important tool for atomistic simulations in many fields, from chemistry via molecular biology to materials science. Most of the established methods, however, rely on local properties and are thus unable to take global changes in the electronic structure into account, which result from long-range charge transfer or different charge states. In this work we overcome this limitation by introducing a fourth-generation high-dimensional neural network potential that combines a charge equilibration scheme employing environment-dependent atomic electronegativities with accurate atomic energies. The method, which is able to correctly describe global charge distributions in arbitrary systems, yields much improved energies and substantially extends the applicability of modern machine learning potentials. This is demonstrated for a series of systems representing typical scenarios in chemistry and materials science that are incorrectly described by current methods, while the fourth-generation neural network potential is in excellent agreement with electronic structure calculations.

en: A fourth-generation high-dimensional neural network potential with accurate electrostatics including non-local charge transfer

dft

display_name: dft

machine-learning-potentials

display_name: machine-learning-potentials

non-local-charge-transfer

display_name: non-local-charge-transfer


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

pseudopotentials

display_name: pseudopotentials

quantum-espresso

display_name: quantum-espresso


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

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:
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

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).

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

materialscloud

en: Materials Cloud

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

envi

en: Environment

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: 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

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: 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

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: Hydrogen boride sheet is a recently fabricated boron-based two-dimensional nanosheet. For the interest of using it in electronic and catalytic applications, it is important that it has sufficient chemical stability for common substances. In this case, we investigate its chemical stability in water, a common substance in ambient condition and many applications. The study was done using experimental and first-principles method. This record contains the crystal structures, optimized via first-principles calculations that were used in discussing the various properties and interaction between water and hydrogen boride sheet. Additionally, input files used to calculate for the systems were included to aid in reproducing results of the study.

en: Chemical stability of hydrogen boride nanosheets in water

chemical-stability

display_name: chemical-stability

density-functional-theory

display_name: density-functional-theory

dft

display_name: dft

hydrogen-boride

display_name: hydrogen-boride

nanosheet

display_name: nanosheet

two-dimensional

display_name: two-dimensional


en: Cu nano catalysts are among the most promising candidates to enable the up-conversion of CO₂ by means of electrochemical reduction. Yet, the lack of stability of Cu nano catalysts during electrochemical CO₂ reduction reaction represents a strong limiting factor in enabling their widespread use at the industrial level.  The record gathers data related to the theoretical evaluation of the stability and activity of Cu-rich nano catalysts, in the presence of a second metal, namely Ga, whose amount varies between 5% and 30%.

en: Alloying as a strategy to boost the stability of Copper nanocatalysts during electrochemical CO₂ reduction reaction

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).

cu

display_name: cu


en: There is much current work on metallic glasses (MGs). The field is making rapid advances and has opened up questions of fundamental scientific interest. Metallic glasses are known to suffer from poor formability. Among other methods of improving the mechanical properties of MGs, introducing deformable crystalline phases into MGs is beneficial for enhancing the plastic compliance of MGs. The definition of the principal phase transformations (on heating and on cooling) underlying the feasibility of such a method is the focus of the deposited in situ high-energy XRD data carried out at Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany. This archive entry contains the temporal evolution of the equilibrium and metastable phases on flash-annealing (heating and cooling) and during containerless solidification via electromagnetic levitation with an unprecedented timescale of ~4 ms.

en: In situ high-energy X-ray diffraction of a CuZr-based metallic glass

materialscloud

en: Materials Cloud

containerless-solidification

display_name: containerless-solidification

electromagnetic-levitation

display_name: electromagnetic-levitation

metallic-glasses

display_name: metallic-glasses

phase-transformation-mechanisms

display_name: phase-transformation-mechanisms

synchrotron-xrd

display_name: synchrotron-xrd


en: Torsional stress has a significant impact on the structure and stability of the nucleosome.  RNA polymerase imposes torsional stress on the DNA in chromatin and unwraps the DNA from the nucleosome to access the genetic information encoded in the DNA.  To understand how the torsional stress affects the stability of the nucleosome, we examined the unwrapping of two half superhelical turns of nucleosomal DNA from either end of the DNA under torsional stress with all-atom molecular dynamics simulations.  The free energies for unwrapping the DNA indicate that positive stress that overtwists DNA facilitates a large-scale asymmetric unwrapping of the DNA without a large extension of the DNA.  During the unwrapping, one end of the DNA was dissociated from H3 and H2A-H2B while the other end of the DNA stably remained wrapped.  The detailed analysis indicates that this asymmetric dissociation is facilitated by the geometry and bendability of the DNA under positive stress.  The geometry stabilized the interaction between the major groove of the twisted DNA and the H3 αN-helix, and the straightened DNA destabilized the interaction with H2A-H2B.  Under negative stress, the DNA became more bendable and flexible, which facilitated the binding of the unwrapped DNA to the octamer in a stable state.  Consequently, we conclude that the torsional stress has a significant impact on the affinity of the DNA and the octamer through the inherent nature of the DNA, and can change the accessibility of regulatory proteins.

en: Torsional stress can regulate the unwrapping of two outer half superhelical turns of nucleosomal DNA

envi

en: Environment

bendability

display_name: bendability

dna

display_name: dna

nucleosome

display_name: nucleosome

torsional-stress

display_name: torsional-stress

unwrapping

display_name: unwrapping


en: We present a method to constrain local charge multipoles within density-functional theory. Such multipoles quantify the anisotropy of the local charge distribution around atomic sites and can indicate potential hidden orders. Our method allows selective control of specific multipoles, facilitating a quantitative exploration of the energetic landscape outside of local minima. Thus, it enables a clear distinction between electronically and structurally driven instabilities. We demonstrate the effectiveness of this method by applying it to charge quadrupoles in the prototypical orbitally ordered material KCuF₃. We quantify intersite multipole-multipole interactions as well as the energy-lowering related to the formation of an isolated local quadrupole. We also map out the energy as a function of the size of the local quadrupole moment around its local minimum, enabling quantification of multipole fluctuations around their equilibrium value. Finally, we study charge quadrupoles in the solid solution KCu₁₋ₓZnₓF₃ to characterize the behavior across the tetragonal-to-cubic transition. Our method provides a powerful tool for studying symmetry breaking in materials with coupled electronic and structural instabilities and potentially hidden orders.

en: Exploring energy landscapes of charge multipoles using constrained density functional theory

constrained-dft

display_name: constrained-dft

electronic-instability

display_name: electronic-instability

erc

display_name: erc

multipoles

display_name: multipoles

perovskite

display_name: perovskite


en: The success of all-graphene electronics is severely hindered by the challenging realization and subsequent integration of semiconducting channels and metallic contacts. Here, we comprehensively investigate the electronic transport across width-modulated heterojunctions consisting of a graphene quantum dot of varying lengths and widths embedded in a pair of armchair-edged metallic nanoribbons, of the kind recently fabricated via on-surface synthesis. We show that the presence of the quantum dot enables the opening of a width-dependent transport gap, thereby yielding built-in one-dimensional metal-semiconductor-metal junctions. Furthermore, we find that, in the vicinity of the band edges, the conductance is subject to a smooth transition from an antiresonant to a resonant transport regime upon increasing the channel length. These results are rationalized in terms of a competition between quantum-confinement effects and quantum dot-to-lead coupling. Overall, our work establishes graphene quantum dot nanoarchitectures as appealing platforms to seamlessly integrate gap-tunable semiconducting channels and metallic contacts into an individual nanoribbon, hence realizing self-contained carbon-based electronic devices.

en: Electronic transport across quantum dots in graphene nanoribbons: Toward built-in gap-tunable metal-semiconductor-metal heterojunctions

cscs

display_name: cscs

electronic-transport

display_name: electronic-transport

gnr

display_name: gnr

graphene

display_name: graphene

marvel

display_name: marvel

nanoribbon

display_name: nanoribbon

quantum-dot

display_name: quantum-dot

snsf

display_name: snsf


en: Doped alkaline-earth chalcogenides are interesting photoluminescent materials for opto-electronic applications. It is crucial to have an extended knowledge about the undoped bulk CaS and CaO since all the excited state properties of the doped material heavily depend on it. In this work we investigate the structural parameters, electronic band structures, macroscopic dielectric constants and absorption spectra for CaS and CaO compounds. Their quasi-particle band structure in the GW approximation yields a value of 4.28 eV and 6.02 eV for the indirect theoretical particle gap of CaS and CaO, respectively. The imaginary part of the macroscopic dielectric function e(omega) is computed including excitonic effects through the Bethe–Salpeter equation. The onset of absorption is within 0.1 eV of the experimental one and the calculated spectrum shows a qualitative agreement with experiment. Our computed exciton binding energies are 0.27 eV and 0.40 eV for CaS and CaO, respectively.

en: First-principles and experimental characterization of the electronic and optical properties of CaS and CaO

ab-initio

display_name: ab-initio

absorption-spectrum

display_name: absorption-spectrum

bethesalpeter

display_name: bethesalpeter

calcium-chalcogenides

display_name: calcium-chalcogenides

cao

display_name: cao

cas

display_name: cas

density-functional-theory

display_name: density-functional-theory

exciton

display_name: exciton

first-principles

display_name: first-principles

macroscopic-dielectric-function

display_name: macroscopic-dielectric-function


en: The renormalization of electronic eigenenergies due to electron-phonon interactions (temperature dependence and zero-point motion effect) is important in many materials. We address it in the adiabatic harmonic approximation, based on first principles (e.g., density-functional theory), from different points of view: directly from atomic position fluctuations or, alternatively, from Janak's theorem generalized to the case where the Helmholtz free energy, including the vibrational entropy, is used. We prove their equivalence, based on the usual form of Janak's theorem and on the dynamical equation. We then also place the Allen-Heine-Cardona (AHC) theory of the renormalization in a first-principles context. The AHC theory relies on the rigid-ion approximation, and naturally leads to a self-energy (Fan) contribution and a Debye-Waller contribution. Such a splitting can also be done for the complete harmonic adiabatic expression, in which the rigid-ion approximation is not required. A numerical study within the density-functional perturbation theory framework allows us to compare the AHC theory with frozen-phonon calculations, with or without the rigid-ion approximation. For the two different numerical approaches without non-rigid-ion terms, the agreement is better than 7 μeV in the case of diamond, which represent an agreement to five significant digits. The magnitude of the non-rigid-ion terms in this case is also presented, distinguishing specific phonon modes contributions to different electronic eigenenergies.

en: Temperature dependence of electronic eigenenergies in the adiabatic harmonic approximation

adiabatic-harmonic-approximation

display_name: adiabatic-harmonic-approximation

allen-heine-cardona-theory

display_name: allen-heine-cardona-theory

ceci

display_name: ceci

diamond

display_name: diamond

electron-phonon-coupling

display_name: electron-phonon-coupling

frqnt

display_name: frqnt

frs-fnrs

display_name: frs-fnrs

temperature-dependence

display_name: temperature-dependence

verification-and-validation

display_name: verification-and-validation

zero-point-motion-renormalization

display_name: zero-point-motion-renormalization


en:
We introduce the unification of dynamical mean field theory (DMFT) and linear-scaling density functional theory (DFT), as recently implemented in ONETEP, a linear-scaling DFT package, and TOSCAM, a DMFT toolbox. This code can account for strongly correlated electronic behavior while simultaneously including the effects of the environment, making it ideally suited for studying complex and heterogeneous systems that contain transition metals and lanthanides, such as metalloproteins. We systematically introduce the necessary formalism, which must account for the non-orthogonal basis set used by ONETEP. In order to demonstrate the capabilities of this code, we apply it to carbon monoxide-ligated iron porphyrin and explore the distinctly quantum-mechanical character of the iron 3d electrons during the process of photodissociation.

This archive record contains example input and output files for the DFT, DFT+U, and DFT+DMFT calculations presented in the associated journal article.

en: ONETEP + TOSCAM: uniting dynamical mean field theory and linear-scaling density functional theory

dynamical-mean-field-theory

display_name: dynamical-mean-field-theory

linear-scaling-dft

display_name: linear-scaling-dft


en:
In nodal-line semimetals, linearly dispersing states form Dirac loops in the reciprocal space with a high degree of electron-hole symmetry and a reduced density of states near the Fermi level. The result is reduced electronic screening and enhanced correlations between Dirac quasiparticles. Here we investigate the electronic structure of ZrSiSe, by combining time- and angle-resolved photoelectron spectroscopy with ab initio density functional theory (DFT) complemented by an extended Hubbard model (DFT+U+V) and by time-dependent DFT+U+V. We show that electronic correlations are reduced on an ultrashort timescale by optical excitation of high-energy electrons-hole pairs, which transiently screen the Coulomb interaction. Our findings demonstrate an all-optical method for engineering the band structure of a quantum material.

This record contains the ARPES raw data in txt format used to create the figures in the referenced publication.

en: Light-induced renormalization of the Dirac quasiparticles in the nodal-line semimetal ZrSiSe

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).

electronic-structure

display_name: electronic-structure

erc

display_name: erc

experimental

display_name: experimental

snsf

display_name: snsf

topological-materials

display_name: topological-materials

trarpes

display_name: trarpes


en: The ethanol steam reforming reaction, together with the adsorption and decomposition of ethanol was studied on CeO2 and gallium-doped ceria (CeGaOx) by a combined experimental and theoretical approach using infrared spectroscopy (IR), mass spectrometry (MS) and density functional theory (DFT) calculations. At 100 °C, different types of monodentate ethoxy species were identified as standing-up (SU) on Ce4+ and lying-down (LD) on Ce4+ and Ga3+, with the alkyl chain more perpendicular or parallel to the surface, respectively. It is suggested that the incorporation of Ga into the ceria lattice changes the decomposition pathway of LD species, which converts to acetate instead of ethylene, attributed to the increased lattice oxygen lability in the Ce―O―Ga interface upon doping and the propensity to form Ga―H surface species. Under ethanol steam reforming conditions, Ga doping of ceria-based materials has a drastic effect by improving the H2:CO2 ratio, changing the product distribution and reducing coke formation.

en: Controlled selectivity for ethanol steam reforming reaction over doped CeO2 surfaces: The role of gallium

materialscloud

en: Materials Cloud

bioethanol

display_name: bioethanol

coke-precursors

display_name: coke-precursors

deactivation

display_name: deactivation

gallia

display_name: gallia

hydrogen-production

display_name: hydrogen-production

prace

display_name: prace


en: Fractionalization is a phenomenon in which strong interactions in a quantum system drive the emergence of excitations with quantum numbers that are absent in the building blocks. Outstanding examples are excitations with charge e/3 in the fractional quantum Hall effect, solitons in one-dimensional conducting polymers and Majorana states in topological superconductors. Fractionalization is also predicted to manifest itself in low-dimensional quantum magnets, such as one-dimensional antiferromagnetic S = 1 chains. The fundamental features of this system are gapped excitations in the bulk and, remarkably, S = 1/2 edge states at the chain termini, leading to a four-fold degenerate ground state that reflects the underlying symmetry-protected topological order. This record contains data to support the result in a recent publication of ours where we use on-surface synthesis to fabricate one-dimensional spin chains that contain the S = 1 polycyclic aromatic hydrocarbon triangulene as the building block. Using scanning tunneling microscopy and spectroscopy at 4.5 K, we probe length-dependent magnetic excitations at the atomic scale in both open-ended and cyclic spin chains, and directly observe gapped spin excitations and fractional edge states therein. Exact diagonalization calculations provide conclusive evidence that the spin chains are described by the S = 1 bilinear-biquadratic Hamiltonian in the Haldane symmetry-protected topological phase. Our results open a bottom-up approach to study strongly correlated phases in purely organic materials, with the potential for the realization of measurement-based quantum computation.

en: Observation of fractional edge excitations in nanographene spin chains

envi

en: Environment

cscs

display_name: cscs

fractionalization

display_name: fractionalization

graphene-flagship

display_name: graphene-flagship

nanographene

display_name: nanographene

spin-chains

display_name: spin-chains


en: High-strength metal alloys achieve their performance via careful control of precipitates and solutes. The nucleation, growth, and kinetics of precipitation, and the resulting mechanical properties, are inherently atomic-scale phenomena, particularly during early-stage nucleation and growth.  Atomistic modeling using interatomic potentials is a desirable tool for understanding the detailed phenomena involved in precipitation and strengthening, which requires length and time scales far larger than those accessible by first-principles methods.  Current interatomic potentials for alloys are not, however, sufficiently accurate for such studies.  Here, a family of neural-network potentials (NNPs) for the Al-Cu system is presented as a first example of a machine-learning potential that can achieve near-first-principles accuracy for many different metallurgically-important aspects of this alloy.  High fidelity predictions of intermetallic compounds, elastic constants, dilute solid-solution energetics, precipitate/matrix interfaces, generalized stacking fault energies, and surfaces for slip in matrix and precipitates, antisite defect energies, and other quantities, are shown.  The NNPs also capture the subtle entropically-induced transition between θ' and θ at temperatures around 600K.  Many comparisons are made with the state-of-the-art Angular-Dependent Potential for Al-Cu, demonstrating the significant quantitative benefit of a machine-learning approach.  A preliminary kinetic Monte Carlo study shows the NNP to predict the emergence of GP zones in Al 4%Cu at T=300K in agreement with experiments.  The NNP shows some significant transferability to defects and properties outside the structures used to develop the NNP but also shows some errors, highlighting that the use of any interatomic potential requires careful validation in application to specific metallurgical problems of interest.

en: Machine learning for metallurgy: a neural network potential for Al-Cu

aluminum

display_name: aluminum

machine-learning

display_name: machine-learning

metallurgy

display_name: metallurgy


en: We determine the band alignment at the CaF2/Si(111) interface through various advanced electronic-structure methods. This interface is experimentally well-studied and serves as an ideal test case to examine the accuracy of theoretical schemes. We use both global and range-separated hybrid functionals as well as GW calculations including self-consistency and vertex corrections. Our calculation procedure accounts for residual strain resulting from the small mismatch in the lateral lattice constants at the interface to minimize the systematic error in the comparison with experiment. Both the hybrid-functional and the GW schemes give band alignments in overall good agreement with the experimental characterization. However, the considered methods yield sizable variations in the calculated band offsets, which do not originate from incorrect evaluations of the band gaps but rather from different inherent relative positions of the band edges. The comparison with experiment reveals that the global hybrid functional and the quasiparticle self-consistent GW with vertex corrections give the most accurate description of the band alignment. We then determine the variation of the band offsets as a function of the amount of excess fluorine at the interface and attribute the experimental spread in the measured offsets to uncontrolled fluorine contamination.

en: Band alignment at the CaF2/Si(111) interface through advanced electronic structure calculations

band-alignment

display_name: band-alignment

density-functional-theory

display_name: density-functional-theory

epfl

display_name: epfl

epitaxial-growth

display_name: epitaxial-growth

gw-method

display_name: gw-method

hybrid-functional

display_name: hybrid-functional

narrow-band-gap-system

display_name: narrow-band-gap-system

snsf

display_name: snsf

wide-band-gap-system

display_name: wide-band-gap-system


en:
This data set contains atomic structures of water clusters, bulk water and rock-salt Li8Mo2Ni7Ti7O32 in the XCrySDen [1] structure format (XSF), and total energies are included as additional meta information. The extended XSF format is compatible with the atomic energy network (aenet) package [2,3] for artificial neural network potential construction and application.  The structures were generated using ab initio molecular dynamics (AIMD) simulations performed with the Vienna Ab Initio Simulation Package (VASP) [4,5] and projector-augmented wave (PAW) [6] pseudopontentials.

For the bulk water system the revised Perdew-Burke-Ernzerhof density functional [7] with the Grimme D3 van-der-Waals correction [8] (revPBE+D3) was used. The AIMD simulations of the Li-Mo-Ni-Ti-O system employed the strongly constrained and appropriately normed (SCAN) semilocal density functional [9].  For both periodic systems, the plane-wave cutoff was 400 eV, and Gamma-point only k-point meshes were employed.  A time step of 1 fs was used for the integration of the equation of motion, and a Nosé-Hoover thermostat [10,11] was used to maintain the temperature at 400 K.

The energies and interatomic forces of the water cluster structures were calculated using the BLYP density functional [12,13] with additional Grimme D3 correction as implemented in the Turbomole software [14].

Further details can be found in the associated research article.

[1] A. Kokalj, J. Mol. Graphics Modell. 17, 176–179 (1999).
[2] N. Artrith, A. Urban, Comput. Mater. Sci. 114, 135–150 (2016).
[3] N. Artrith, A. Urban, G. Ceder, Phys. Rev. B 96, 014112 (2017).
[4] G. Kresse, J. Furthmüller, Phys. Rev. B 54, 11169–11186 (1996).
[5] Kresse, J. Furthmüller, Comput. Mater. Sci. 6, 15–50 (1996).
[6] P. E. Blöchl, Phys. Rev. B 50, 17953–17979 (1994).
[7] Y. Zhang, W. Yang, Phys. Rev. Lett. 80, 890–890 (1998).
[8] S. Grimme, J. Antony, S. Ehrlich, H. Krieg, J. Chem. Phys. 132, 154104 (2010).
[9] J. Sun, A. Ruzsinszky, J. Perdew, Phys. Rev. Lett. 115, 036402 (2015).
[10] S. Nosé, J. Chem. Phys. 81, 511–519 (1984).
[11] W. G. Hoover, Phys. Rev. A 31, 1695–1697 (1985).
[12] A. D. Becke, Phys. Rev. A 38, 3098–3100 (1988).
[13] C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 37, 785–789 (1988).
[14] F. Furche, R. Ahlrichs, C. Hättig, W. Klopper, M. Sierka, F. Weigend, WIREs Comput Mol Sci 4, 91–100 (2014).

en: Efficient Training of ANN Potentials by Including Atomic Forces via Taylor Expansion and Application to Water and a Transition-Metal Oxide

aenet

display_name: aenet

aimd

display_name: aimd

lithium-transition-metal-oxide

display_name: lithium-transition-metal-oxide

vasp

display_name: vasp

water

display_name: water


en: In this record we provide data to support our recent work on the synthesis of oligo(indenoindene). Fully conjugated ladder polymers (CLP) possess unique optical and electronic properties and are considered promising materials for applications in (opto)electronic devices. Poly(indenoindene) is a CLP consisting of an alternating array of five- and six-membered rings, which has remained elusive so far. Our results relate to on-surface synthesis of oligo(indenoindene) on Au(111). Its structure and a low electronic band gap have been elucidated by low-temperature scanning tunneling microscopy and spectroscopy and noncontact atomic force microscopy, complemented by density functional theory calculations. Achieving defect-free segments of oligo(indenoindene) offers exclusive insight into this CLP and provides the basis to further synthetic approaches.

en: On-surface synthesis of oligo(indenoindene)

alkyls

display_name: alkyls

cscs

display_name: cscs

oligomers

display_name: oligomers

polymers

display_name: polymers


en: Accurate prediction of gas solubility in a liquid is crucial in many areas of chemistry, and a detailed understanding of the molecular mechanism of the gas solvation continues to be an active area of research. Here, we extend the idea of the constant chemical potential molecular dynamics (CμMD) approach to the calculation of the gas solubility in the liquid under constant gas chemical potential conditions. As a representative example, we utilize this method to calculate the isothermal solubility of carbon dioxide in water. Additionally, we provide microscopic insight into the mechanism of solvation that preferentially occurs in areas of the surface where the hydrogen network is broken.

en: Molecular mechanism of gas solubility in liquid: constant chemical potential molecular dynamics simulations

constant-chemical-potential-simulations

display_name: constant-chemical-potential-simulations

erc

display_name: erc

solution

display_name: solution


en: Donor-acceptor (D-A) extended copolymers have shown great potential to be exploited for intramolecular Singlet Fission (iSF) because of their modular tunability and intrinsic ability to incorporate low-lying charge-transfer (CT) and a triplet-pair (TT) state. While the SF mechanism has been widely debated in homo- and hetero-dimers, little is known about the singlet splitting process in A-D-A copolymer trimers. Unlike traditional two-sites SF, the process of iSF in D-A copolymers involves three molecular units consisting of two A and one D following a A-D-A polymeric chain. This scenario is therefore, different from the homo-dimer analogous in terms of which states (if any) may drive the SF process. In this work, we identify how singlet splitting occurs in prototypical iSF D-A copolymer poly(benzodithiophene-alt-thiophene-1,1-dioxide) (BDT−TDO) by means of wave-packet propagations on the basis of the Linear Vibronic Coupling (LVC) model Hamiltonian. Our results reveal that three different mechanisms drive the S→TT population transfer via antisymmetric and symmetric vibrational motion, including two favorable mechanisms of direct and mediated interactions, as well as a parasitic decay pathway that potentially delays the process. Remarkably, we uncover the interplay between an upper state of marked multi-excitonic character and a low-lying CT state in balancing the splitting efficiency, which anticipates their major role in defining future guidelines for the molecular design of D-A copolymers for iSF.

en: Direct, mediated and delayed intramolecular singlet fission mechanism in donor-acceptor copolymers

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).

donor-acceptor-copolymers

display_name: donor-acceptor-copolymers

epfl

display_name: epfl

lvc-model

display_name: lvc-model

quantum-dynamics

display_name: quantum-dynamics

singlet-fission

display_name: singlet-fission


en: We theoretically investigate the electron transport in armchair and zigzag graphene nanoribbons (GNRs) chemically functionalized with p-polyphenyl and polyacene groups of increasing length. Our nearest-neighbor tight-binding calculations indicate that, depending on whether the number of aromatic rings in the functional group is even or odd, the resulting conductance at energies matching the energy levels of the corresponding isolated molecule is either unaffected or reduced by exactly one quantum as compared to the pristine GNR, respectively. Such an even–odd effect is shown to originate from a subtle interplay between the electronic states of the guest molecule that are spatially localized on the binding sites and those of the host nanoribbon. We next generalize our findings by employing more accurate tight-binding Hamiltonians along with density-functional theory calculations and critically discuss the robustness of the observed physical effects against the level of theory adopted. Our work offers a comprehensive understanding of the influence of aromatic molecules bound to the edge of graphene nanoribbons on their electronic transport properties, an issue which is instrumental to the prospective realization of graphene-based chemosensors.

en: Even–odd conductance effect in graphene nanoribbons induced by edge functionalization with aromatic molecules: basis for novel chemosensors

materialscloud

en: Materials Cloud

electronic-transport

display_name: electronic-transport

gnr

display_name: gnr

graphene

display_name: graphene

marvel

display_name: marvel

nanoribbon

display_name: nanoribbon

sensor

display_name: sensor

snsf

display_name: snsf


en: Molecular dipole moments of the QM7b dataset, a random sample of 21'000 molecules from the QM9 dataset, and the MuML showcase set (including the four challenge series) described in the linked publication.

en: Quantum mechanical dipole moments in the QM7b, 21k molecules of QM9, and MuML showcase datasets

envi

en: Environment

ccsd

display_name: ccsd

dft

display_name: dft

molecular-dipole

display_name: molecular-dipole


en: Lead-halide perovskite (LHP) semiconductors are emergent optoelectronic materials with outstanding transport properties which are not yet fully understood. We find signatures of large polaron formation in the electronic structure of the inorganic LHP CsPbBr3 by means of angle-resolved photoelectron spectroscopy. The experimental valence band dispersion shows a hole effective mass of 0.26±0.02 me, 50% heavier than the bare mass m0=0.17 me predicted by ab-initio calculations. Calculations of the electron-phonon coupling indicate that phonon dressing of the carriers mainly occurs via distortions of the Pb-Br bond with a Fröhlich coupling parameter α=1.82. A good agreement between theoretical and experimental data is obtained within the Feynman polaron model, validating a viable theoretical method to predict the carrier effective mass of LHPs ab initio.

en: Evidence of large polarons in photoemission band mapping of the perovskite semiconductor CsPbBr3

density-functional-theory

display_name: density-functional-theory

electron-phonon-coupling

display_name: electron-phonon-coupling

erc

display_name: erc

frohilch-polarons

display_name: frohilch-polarons

gw-method

display_name: gw-method

hybrid-functionals

display_name: hybrid-functionals

lead-halide-perovskites

display_name: lead-halide-perovskites


en: Halide perovskites constitute a new class of semiconductors that hold promise for low-cost solar cells and optoelectronics. One key property of these materials is the electron mobility, which determines the average electron speed due to a driving electric field. Here we elucidate the atomic-scale mechanisms and theoretical limits of carrier mobilities in halide perovskites by performing a comparative analysis of the archetypal compound CH₃NH₃PbI₃, its inorganic counterpart CsPbI₃, and a classic semiconductor for light-emitting diodes, wurtzite GaN, using cutting-edge many-body ab initio calculations. We demonstrate that low-energy longitudinal-optical phonons associated with fluctuations of the Pb−I bonds ultimately limit the mobility to 80 cm² /(V s) at room temperature. By extending our analysis to a broad class of compounds, we identify a universal scaling law for the carrier mobility in halide perovskites, and we establish the design principles to realize high-mobility materials.

en: Origin of low carrier mobilities in halide perovskites

ab-initio

display_name: ab-initio

carrier-transport

display_name: carrier-transport

first-principles

display_name: first-principles

gan

display_name: gan

halide-perovskites

display_name: halide-perovskites

mobility

display_name: mobility

perovskites

display_name: perovskites

prace

display_name: prace


en:
The record contains the data to support the findings of our recent work on reversibility of the dehalogenation process in on-surface aryl-aryl coupling.
In the emerging field of on‐surface synthesis, dehalogenative aryl–aryl coupling is unarguably the most prominent tool for the fabrication of covalently bonded carbon‐based nanomaterials. Despite its importance, the reaction kinetics are still poorly understood. Here we present a comprehensive temperature‐programmed x‐ray photoelectron spectroscopy investigation of reaction kinetics and energetics in the prototypical on‐surface dehalogenative polymerization of 4,4′′‐dibromo‐p‐terphenyl into poly(para‐phenylene) on two coinage metal surfaces, Cu(111) and Au(111). We find clear evidence for reversible dehalogenation on Au(111), which is inhibited on Cu(111) owing to the formation of organometallic intermediates. The incorporation of reversible dehalogenation in the reaction rate equations leads to excellent agreement with experimental data and allows extracting the relevant energy barriers. Our findings deepen the mechanistic understanding and call for its reassessment for surface‐confined aryl–aryl coupling on the most frequently used metal substrates.

en: Reversible dehalogenation in on-surface aryl-aryl coupling

aryl-aryl-coupling

display_name: aryl-aryl-coupling

dehalogenation

display_name: dehalogenation

experimental

display_name: experimental

onr

display_name: onr

snsf

display_name: snsf

surface-chemistry

display_name: surface-chemistry


en: We explore the interplay between ferroelectricity and metallicity, which are generally considered to be contra-indicated properties, in the prototypical ferroelectric barium titanate, BaTiO3. Using first-principles density functional theory, we calculate the effects of electron and hole doping, first by introducing a hypothetical background charge, and second through the introduction of explicit impurities (La, Nb and V for electron doping, and K, Al and Sc for hole doping). We find that, apart from a surprising increase in polarization at small hole concentrations, both charge-carrier types decrease the tendency towards ferroelectricity, with the strength of the polarization suppression, which is different for electrons and holes, determined by the detailed structure of the conduction and valence bands. Doping with impurity atoms increases the complexity and allows us to identify three factors that influence the ferroelectricity: structural effects arising largely from the size of the impurity ion, electronic effects from the introduction of charge carriers, and changes in unit-cell volume and shape. A competing balance between these contributions can result in an increase or decrease in ferroelectricity with doping.

en: Interplay between ferroelectricity and metallicity in BaTiO3

dft

display_name: dft

ferroelectricity

display_name: ferroelectricity

marvel-inspire

display_name: marvel-inspire


en: The study of chemical reactions in aqueous media is very important for its implications in several fields of science, from biology to industrial processes. However, modeling these reactions is difficult when water directly participates in the reaction, since it requires a fully quantum mechanical description of the system. Ab-initio molecular dynamics is the ideal candidate to shed light on these processes. However, its scope is limited by a high computational cost. A popular alternative is to perform molecular dynamics simulations powered by machine learning potentials, trained on an extensive set of quantum mechanical calculations. Doing so reliably for reactive processes is difficult because it requires including very many intermediate and transition state configurations. In this study we used an active learning procedure accelerated by enhanced sampling to harvest such structures and to build a neural-network potential to study the urea decomposition process in water. This allowed us to obtain the free energy profiles of this important reaction in a wide range of temperatures, to discover several novel metastable states, and improve the accuracy of the kinetic rates calculations. Furthermore, we found that the formation of the zwitterionic intermediate has the same probability of occurring via an acidic or a basic pathway, which could be the cause of the insensitivity of reaction rates to the solution pH.

en: Using metadynamics to build neural network potentials for reactive events: the case of urea decomposition in water

erc

display_name: erc

free-energy-surface

display_name: free-energy-surface

kinetic-rates

display_name: kinetic-rates

metadynamics

display_name: metadynamics

neural-network-potentials

display_name: neural-network-potentials

urea-decomposition

display_name: urea-decomposition


en: In the record we provide the inputs and outputs for the calculations that support our recent results in the synthesis of pentagon-fused graphene nanoribbons (GNRs). GNRs have potential for applications in electronic devices. A key issue, thereby, is the fine-tuning of their electronic characteristics, which can be achieved through subtle structural modifications. These are not limited to the conventional armchair, zigzag, and cove edges, but also possible through incorporation of non-hexagonal rings. On-surface synthesis enables the fabrication and visualization of GNRs with atomically precise chemical structures, but strategies for the incorporation of non-hexagonal rings have been underexplored. In the manuscript, we describe the on-surface synthesis of armchair-edged GNRs with incorporated five-membered rings through the C-H activation and cyclization of benzylic methyl groups. ortho-Tolyl-substituted dibromobianthryl was employed as the precursor monomer, and visualization of the resulting structures after annealing at 300 °C on a gold surface by high-resolution noncontact atomic force microscopy clearly revealed the formation of methylene-bridged pentagons at the GNR edges. These persisted after annealing at 340 °C, along with a few fully conjugated pentagons having singly-hydrogenated apexes. The benzylic methyl groups could also migrate or cleave-off, resulting in defects lacking the five-membered rings. Moreover, unexpected and unique structural rearrangements, including the formation of embedded heptagons, were observed, providing novel insights into the on-surface reactions en route to functional carbon nanomaterials.

en: On-surface activation of benzylic C-H bonds for the synthesis of pentagon-fused graphene nanoribbons

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-calculations

display_name: ab-initio-calculations

carbon-based-nanomaterials

display_name: carbon-based-nanomaterials

graphene-flagship

display_name: graphene-flagship

graphene-nanoribbons

display_name: graphene-nanoribbons

on-surface-synthesis

display_name: on-surface-synthesis


en: Knowledge of the structure of amorphous solids can direct, for example, the optimization of pharmaceutical formulations, but atomic-level structure determination in amorphous molecular solids has so far not been possible. Solid-state NMR is among the most popular methods to characterize amorphous materials, and Molecular Dynamics (MD) simulations can help describe the structure of disordered materials. However, directly relating MD to NMR experiments in molecular solids has been out of reach until now because of the large size of these simulations. Here, using a machine learning model of chemical shifts, we determine the atomic-level structure of the hydrated amorphous drug AZD5718 by combining dynamic nuclear polarization-enhanced solid-state NMR experiments with predicted chemical shifts for MD simulations of large systems. From these amorphous structures we then identify H-bonding motifs and relate them to local intermolecular complex formation energies.

en: Structure determination of an amorphous drug through large-scale NMR predictions

materialscloud

en: Materials Cloud

experimental

display_name: experimental

machine-learning

display_name: machine-learning

molecular-dynamics

display_name: molecular-dynamics

nmr

display_name: nmr


en: The on-top pair density [Π(r)] is a local quantum chemical property, which reflects the probability of two electrons of any spin to occupy the same position in space. Simplest quantity related to the two-particles density matrix, the on-top pair density is a powerful indicator of electron correlation effects and, as such, it has been extensively used to combine density functional theory and multireference wavefunction theory. The widespread application of Π(r) is currently hindered by the need for post-Hartree-Fock or multireference computations for its accurate evaluation. In this work, we propose the construction of a machine learning model capable of predicting the CASSCF-quality on-top pair density of a molecule only from its structure and composition. Our model, trained on the GDB11-AD-3165 database, is able to predict with minimal error the on-top pair density of organic molecules bypassing completely the need for ab-initio computations. The accuracy of the regression is demonstrated using the on-top ratio as a visual metric of electron correlation effects and bond-breaking in real-space. In addition, we report the construction of a specialized basis set, built to fit the on-top pair density in a single, atom-centered expansion. This basis, cornerstone of the regression, could be potentially used also in the same spirit of the resolution-of-the-identity approximation for the electron density.

en: Learning on-top: regressing the on-top pair density for real-space visualization of electron correlation

envi

en: Environment

epfl

display_name: epfl

on-top-pair-density

display_name: on-top-pair-density

snsf

display_name: snsf

strong-electron-correlation

display_name: strong-electron-correlation


en: We study the phase equilibrium between liquid water and ice Ih modeled by the TIP4P/Ice interatomic potential using enhanced sampling molecular dynamics simulations. Our approach is based on the calculation of ice Ih-liquid free energy differences from simulations that visit reversibly both phases. The reversible interconversion is achieved by introducing a static bias potential as a function of an order parameter. The order parameter was tailored to crystallize the hexagonal diamond structure of oxygen in ice Ih. We analyze the effect of the system size on the ice Ih-liquid free energy differences, and we obtain a melting temperature of 270 K in the thermodynamic limit. This result is in agreement with estimates from thermodynamic integration (272 K) and coexistence simulations (270 K). Since the order parameter does not include information about the coordinates of the protons, the spontaneously formed solid configurations contain proton disorder as expected for ice Ih.

en: Phase equilibrium of liquid water and hexagonal ice from enhanced sampling molecular dynamics simulations

enhanced-sampling

display_name: enhanced-sampling

free-energy

display_name: free-energy

ice

display_name: ice

proton-disorder

display_name: proton-disorder

water

display_name: water


en: The fundamental band gaps of liquid water and hexagonal ice are calculated through advanced electronic-structure methods. We compare specifically the performance of state-of-the-art GW calculations with nonempirical hybrid functionals. For the latter, we fix the free parameters either through the dielectric response of the material or through enforcing Koopmans' condition to localized states. The various approaches yield consistent band gaps, in good agreement with available experimental references. Furthermore, we discuss the critical aspects of each approach that underlie the band-gap predictions.

en: Band gaps of liquid water and hexagonal ice through advanced electronic-structure calculations

band-gap

display_name: band-gap

first-principles

display_name: first-principles

hexagonal-ice

display_name: hexagonal-ice

liquid-water

display_name: liquid-water

nonempirical-hybrid-functionals

display_name: nonempirical-hybrid-functionals


en: This record contains all the raw data in the paper Nature Communications volume 12, Article number: 3994 (2021). Constrained by the Nielsen-Ninomiya no-go theorem, in all so-far experimentally determined Weyl semimetals (WSMs) the Weyl points (WPs) always appear in pairs in the momentum space with no exception. As a consequence, Fermi arcs occur on surfaces which connect the projections of the WPs with opposite chiral charges. However, this situation can be circumvented in the case of unpaired WP, without relevant surface Fermi arc connecting its surface projection, appearing singularly, while its Berry curvature field is absorbed by nontrivial charged nodal walls. Here, combining angle-resolved photoemission spectroscopy with density functional theory calculations, we show experimentally that a singular Weyl point emerges in PtGa at the center of the Brillouin zone (BZ), which is surrounded by closed Weyl nodal walls located at the BZ boundaries and there is no Fermi arc connecting its surface projection. Our results reveal that nontrivial band crossings of different dimensionalities can emerge concomitantly in condensed matter, while their coexistence ensures the net topological charge of different dimensional topological objects to be zero. Our observation extends the applicable range of the original Nielsen-Ninomiya no-go theorem which was derived from zero dimensional paired WPs with opposite chirality. The ARPES data, calculated band structure, and related documents are attached in this record.

en: Observation of a singular Weyl point surrounded by charged nodal walls in PtGa

unpaired-weyl-points

display_name: unpaired-weyl-points

weyl-nodal-plane

display_name: weyl-nodal-plane

weyl-nodal-surface

display_name: weyl-nodal-surface


en: A computationally efficient workflow for obtaining low-energy tight-binding Hamiltonians for twisted bilayer graphene, obeying both crystal and time-reversal symmetries is presented in this work. The Hamiltonians at the first magic angle are generated using the Slater-Koster approach with parameters obtained by a fit to ab-initio data at larger angles. Low-energy symmetric four-band and twelve-band Hamiltonians are constructed using the Wannier90 software. The advantage of our scheme is that the low-energy Hamiltonians are purely real and are obtained with the maximum-localization procedure to reduce the spread of the basis functions. Finally, we compute extended Hubbard parameters for both models within the constrained random phase approximation (cRPA) for screening, which again respect the symmetries. The workflow is straightforwardly transferable to other twisted multi-layer materials.

en: Four- and twelve-band low-energy symmetric Hamiltonians and Hubbard parameters for twisted bilayer graphene using ab-initio input

crpa

display_name: crpa

erc

display_name: erc

hubbard-parameters

display_name: hubbard-parameters

magic-angle

display_name: magic-angle

slater-koster

display_name: slater-koster

tight-binding

display_name: tight-binding

twisted-bilayer-graphene

display_name: twisted-bilayer-graphene

wannierization

display_name: wannierization


en: Azulene, the smallest neutral nonalternant aromatic hydrocarbon, serves not only as a prototype for fundamental studies but also as a versatile building block for functional materials because of its unique opto(electronic) properties. The record contains data to support our recent work where we report the on-surface synthesis and characterization of the homopolymer of azulene connected exclusively at the 2,6-positions using 2,6-diiodoazulene as the monomer precursor. Properties of carbon-based aromatic systems are sensitively determined by their bond topologies. So far, much attention has been paid to the design and synthesis of aromatic materials like conjugated polymers and nanographenes constituted by alternant hydrocarbons, which do not possess odd-membered rings. In contrast, incorporation of non-alternant hydrocarbons has only rarely been explored.

en: On-surface synthesis of polyazulene with 2,6-connectivity

ab-initio

display_name: ab-initio

azulene

display_name: azulene

on-surface-synthesis

display_name: on-surface-synthesis

snsf

display_name: snsf


en:
Trigonal tellurium, a small-gap semiconductor with pronounced magneto-electric and magneto-optical responses, is among the simplest realizations of a chiral crystal. We have studied by spin- and angle-resolved photoelectron spectroscopy its unconventional electronic structure and unique spin texture. We identify Kramers–Weyl, composite, and accordionlike Weyl fermions, so far only predicted by theory, and show that the spin polarization is parallel to the wave vector along the lines in k space connecting high-symmetry points. Our results clarify the symmetries that enforce such spin texture in a chiral crystal, thus bringing new insight in the formation of a spin vectorial field more complex than the previously proposed hedgehog configuration. Our findings thus pave the way to a classification scheme for these exotic spin textures and their search in chiral crystals.

This records refers to the experimental data shown in the referenced article, saved as txt files along with a metadata descriptor file.

en: Radial spin texture of the Weyl fermions in chiral tellurium

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).

chirality

display_name: chirality

experimental

display_name: experimental

spinarpes

display_name: spinarpes

topological-materials

display_name: topological-materials


en: The development of rechargeable batteries based on a Ca metal anode demands the identification of suitable cathode materials. This work investigates the potential application of a variety of compounds, which are selected from the In-organic Crystal Structural Database (ICSD) considering 3d-transition metal oxysulphides, pyrophosphates, silicates, nitrides, and phosphates with a maximum of four different chemical elements in their composition. Cathode perfor-mance of CaFeSO, CaCoSO, CaNiN, Ca3MnN3, Ca2Fe(Si2O7), CaM(P2O7) (M = V, Cr, Mn, Fe, Co), CaV2(P2O7)2, Ca(VO)2(PO4)2 and α-VOPO4 is evaluated throughout the calculation of operation voltages, volume changes associated to the redox reaction and mobility of Ca2+ ions. Some materials exhibit attractive specific capacities and intercalation voltages combined with energy barriers for Ca migration around 1 eV (CaFeSO, Ca2FeSi2O7 and CaV2(P2O7)2). Based on the DFT results, αI-VOPO4 is identified as a potential Ca-cathode with a maximum theoretical specific capacity of 312 mAh/g, an average intercalation voltage of 2.8 V and calculated energy barriers for Ca migration below 0.65 eV (GGA functional).

en: Enlisting potential cathode materials for rechargeable Ca batteries.

materialscloud

en: Materials Cloud

ca-batteries

display_name: ca-batteries

cathode-materials

display_name: cathode-materials

neb

display_name: neb

vasp

display_name: vasp