en: Analyzing the structure and dynamics of the human middle ear is crucial for understanding biomechanics and improving clinical practice; however, characterizing middle ear structures is challenging due to their small sizes, location inside the temporal bone, and minute displacements. Synchrotron radiation-based X-ray microtomography can visualize both the soft and hard tissues of the entire intact middle ear with micrometer resolution. Unfortunately, access to synchrotron radiation facilities is limited and handling the related TB-scale data volumes requires high performance computing infrastructure. Data sharing efforts can increase accessibility and encourage development of new research directions. Here, we share static microtomography datasets covering the entire middle ear and surroundings for 15 fresh-frozen human temporal bones with voxel sizes of 2.75 or 5.8 µm. These datasets allow for the analysis of rich anatomical information across a range of specimens.

en: Static synchrotron X-ray microtomography of 15 intact human middle ears

en: anatomy synchrotron-radiation hearing-research middle-ear x-ray-microtomography

en: PSI Data Catalog


$oid: OBSOLETE

en: Unlocking the finest details of Portland cement hydration has challenged researchers for over a century, as existing 3D imaging techniques struggled to capture the time-dependent processes with sufficient spatial resolution. In this study, we break new grounds by optimising near-field ptychographic X-ray computed tomography to achieve an unprecedented spatial resolution of ≈90 nm, for a thick capillary of 160 μm of diameter. The ratio horizontal field-of-view size to voxel size being 180/0.055=3270. In a first section, it is concluded that 1200 angular projections are sufficient to image 180 m with a spatial resolution of ≈100 nm, which is very important for future 4D studies aimed to decrease the time resolution below 100 min. In a second section, the highest spatial resolution reconstruction is analysed. The nanoimaging study reveals hydration products in their natural state, including calcium-silicate-hydrate (C-S-H) gels of different natures, ettringite needle clusters within C-S-H gel shell and layered and bulk portlandite. Chiefly, quantitative electron densities across different orientations allow to distinguish between inner product and outer product C-S-H gel components. Inner product C-S-H gel has an average electron density of 0.66 e-Å-3 (equivalent to a mass density of 2.12 gcm-3) whereas outer product C-S-H gel has a 22% lower average electron density, 0.52 e-Å-3 or 1.66 gcm-3. According to our measurements, the average ettringite needle is 3(1) µm long and 0.24(5) µm thick. This work advances our understanding of cementitious materials by providing nano-features and densities of hydration products and it will facilitate new possibilities of looking at in situ cement hydration processes.

en: High-resolution nanoimaging study of a cement paste by near-field ptychographic X-ray computed tomography

approval_status: approved

en: The PSI Data Catalog is the central repository directory for scientific metadata generated at the Paul Scherrer Institut (PSI). Powered by SciCat—a community-driven, open-source metadata management framework co-developed by PSI—the catalog provides discoverability and standardized access pathways to petabyte-scale datasets produced across PSI’s large-scale research facilities, including the Swiss Light Source (SLS), the Swiss Spallation Neutron Source (SINQ), and the SwissFEL X-ray free-electron laser.

de: PSI Data Catalog

fr: PSI Data Catalog

it: PSI Data Catalog

political_level: other

state: active

type: organization

psi

capacity: public

de: PSI Open Data Provider

type: dataset

key: guid

key: uri

value: DCAT Harvester SciCat

envi

de: Umwelt

en: Environment

fr: Environnement

it: Ambiente


en: In the associated article to these datasets, we investigate the effect of lossy compression of original X-ray projections onto the final tomographic reconstructions. We demonstrate that a compression factor of at least 3-4x does generally not impact the reconstruction quality. Potentially, compression with this factor could therefore be used in a transparent way to the user community for instance prior to data archiving. Higher factors (6-8x) can be achieved for tomographic volumes with a high signal-to-noise ratio as it is the case for phase retrieved datasets.

en: Selection of representative datasets for data compression investigations


en:
n this work, we introduce the first single-photon-counting hybrid pixel detec-27
tor capable of detecting X-ray energies as low as 550 eV, utilizing the internal28
amplification of Low-Gain Avalanche Diode (LGAD) sensors. This detector is29
thoroughly characterized in terms of Signal-to-Noise Ratio and Detective Quan-30
tum Efficiency. We demonstrate its capabilities through ptychographic imaging31
at MAX IV 4th generation synchrotron light source at the Fe L3-edge (707 eV),32
showcasing the enhanced detection performance of the system. This development33
sets a new benchmark for soft X-ray applications at synchrotrons, paving the way34
for significant advancements in imaging and analysis at lower photon energies.

en: Single-photon counting pixel detector for soft X-rays - raw data


en: The associated article to these datasets describes a new genus and two new species from the Late Cretaceous (Campanian-Maastrichtian) Mira locality, District of Coimbra, Portugal. The new taxa are based on small lignitized and charcoalified flower buds, post-anthetic flowers and a fruit. Internal structures of the fossils were investigated using synchrotron radiation X-ray tomographic microscopy at the TOMCAT Beamline, Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland. Internal structures and other details provide clear evidence for a phylogenetic position of the fossils in the family Primulaceae of the order Ericales. A key distinctive feature that is critical for placing the fossils in the Primulaceae s. l., is the free, central dome-shaped placenta that bears numerous, densely spaced ovules. The fruit matured into a capsule containing many, minute, reticulate seeds. Phylogenetic analyses using external and internal features of the fossils confirm their relationship to Primulaceae s. l. and indicate a position as sister to the genus Samolus of the subfamily Theophrastoideae. The occurrence of these fossils in the Late Cretaceous calls into question a previous hypothesis that the Theophrastoideae originated in the Neotropics and dispersed relatively recently into other regions.

en: Synchrotron radiation X-ray tomographic microscopy datasets for primuloid flowers from the Late Cretaceous of Portugal


en: The article associated with these data collection describes the development of an image analysis pipeline suitable for analysis of all airspaces of an entire mouse lung. The classical stereology contributed to understanding the lung structure of the healthy and homogeneous lung, but has its limit in the analysis of heterogeneous structures such as diseased lung. Expanding stereology to the entire lung volume will allow for better comprehension of unevenly distributed lung damage. The proposed pipeline consists of several steps and starts with (i) image acquisition with high-resolution synchrotron radiation-based X-ray tomographic microscopy, as well as reconstruction and stitching of the individual scans, followed by (ii) image segmentation with free machine learning tool ilastik and ImageJ and (iii) calculation of the airspace diameter distribution with the thickness map function from the image analysis program pi2. To test the efficacy of the pipeline we analyzed adult mice lungs with cystic fibrosis-like disease or elastase-induced emphysema and their littermate controls. We were able to separately analyze two main lung compartments, the conducting airways and gas-exchange area. The distribution of airspace dimeters indicates the presence of enlarged lung airspaces in both compartments for both disease models. Finally, comparable results were obtained when applying the pipeline to images acquired with μCT, suggesting that our pipeline is applicable to a broader range of imaging modalities.

en: Airspace diameter map - a quantitative measurement of all pulmonary airspaces to characterize structural lung diseases


en: The article linked to the datasets provided here describes a diverse assemblage of fossil mosses retrieved from the Early Cretaceous Catefica mesofossil flora, Portugal. The Catefica mesofossil flora is mainly dominated by angiosperm remains such as flowers, fruits and seeds. Mosses constitute a minor part of the flora. However, the mosses are systematically varied and informative, and they add important new information for understanding the diversification of the group through geological time. The fossil mosses from Catefica comprise three-dimensional charcoalified and lignitized fragments of gametophytes with leaves still attached and a single capsule. Twenty-four specimens were studied at the TOMCAT beamline of the Swiss Light Source of the Paul Scherrer Institute, Villigen, Switzerland. The analyses were carried out using a x10 objective with isotropic pixel size of 0.65 μm (S156534, S156535, S266374–S266379, S266383–S266392) or a x20 objective with isotropic pixel size of 0.325 μm (S171522, S174251, S266084, S266380–S266382). Together with scanning electron microscopy (SEM), the synchrotron radiation X-ray tomographic microscopy (SRXTM) analyses have revealed excellent morphology and cellular details that allow the recognition of seven new, extinct species accommodated in six genera. Three of the species can with confidence be placed in extant genera, while four are assigned to new, extinct genera. The species are distributed among four orders of extant mosses, Sphagnales, Polytrichales, Diphysciales and Dicranales, representing three classes, Sphagnopsida, Polytrichopsida and Bryopsida. Diphysciales being reported from Mesozoic strata for the first time. It is significant that although the Catefica mosses are diverse, they all document the presence of taxa from the basal grade of moss phylogeny, and all fossils belong to lineages that diverged prior to the diversification of the Bryidae, the most diverse clade of living mosses.

en: Synchrotron radiation X-ray tomographic microscopy datasets for Early Cretaceous mosses from the Catefica mesofossil flora, Portugal


en:
This repository contains the complete dataset and associated software supporting the publication:
“In-Situ Ptychographic Nanotomography Captures Activation, Mobility, and Deactivation of Supported Catalysts”

The data were acquired using in-situ ptychographic X-ray computed nanotomography (PXCT) and used to investigate structural evolution of Pd-on-silica catalysts under methane oxidation conditions.
Experiments were performed at the cSAXS beamline of the SLS.

The dataset includes raw diffraction data, reconstructed projections, 3D electron density tomograms, and analysis/reconstruction codes.

Codes:
cxs_software_ptychography/  Contains ptychographic reconstruction routines (phase retrieval, scan handling, preprocessing).
cxs_software_tomography/    Contains tomographic reconstruction and 3D volume processing tools.

Raw Data
S03000-03999_ID ...     Raw diffraction datasets acquired during in-situ scanning nanotomography experiments

Reconstructed Data
analysis_S03000-03999 ...    Includes phase and/or amplitude porjection reconstructions
reconstructed_tomograms    Volumetric datasets derived from ptychographic projections used for analysis

en: Data and Software Supporting: In-Situ Ptychographic Nanotomography Captures Activation, Mobility, and Deactivation of Supported Catalysts

heterogeneous-catalysis

display_name: heterogeneous-catalysis

x-ray-ptychography

display_name: x-ray-ptychography

x-ray-tomography

display_name: x-ray-tomography


en:
The extinct plant group Bennettitales (Cycadeoidales) was a prominent part of Mesozoic vegetation. The group has been studied extensively and for more than 100 years it has been central in discussions of the relationships among the major groups of seed plants in which extinct plants were also considered. Despite much effort the phylogenetic position of the Bennettitales is still unresolved with a major obstacle being uncertainty about how to interpret the organisation and structure of the seed. The most widely accepted interpretation has been that the seed, like the seeds of most conifers, has a single integument around the nucellus and lacks any additional coverings. An alternative interpretation is that the seed integument is surrounded by an envelope comparable to the situation in extant Gnetales and extinct Erdtmanithecales. The petrified seed cone of Cycadeoidea (Bennettites) morierei described in the late nineteenth century from the Early Cretaceous of Normandy is one of the most informative bennettitalean reproductive structures with its superb preservation offering great potential for resolving the unsettled discussion regarding seed structure in Bennettitales.
	C. morierei was carefully documented by Octave Lignier in his monumental study “Végétaux fossiles de Normandie. Structure et affinités du Bennettites morierei Sap. & Mar. (sp.)” from 1894, but despite his meticulous analysis of the fossil, Lignier left certain questions open in his interpretation and in his widely cited reconstruction of the structure of the seed. In the paper associated with the datasets provided here we have re-examined fragments of Cycadeoidea morierei using synchrotron X-ray tomographic microscopy (SRXTM) to attempt to answer some of these open questions.
	Cycadeoidea morierei is based on a single petrified seed cone. The specimen was fractured by Lignier, who prepared several thin sections, in longitudinal as well as transverse directions in preparing his account. The original material was stored at the University of Caen, France, but most was lost during the second World War. However, several larger and smaller fragments of the seed cone were later recovered at the university and made available for the present study. Among the fragments studied using SRXTM were small isolated, abraded seeds and interseminal scales (e.g., fragments 6 and 8) and a few small groups of fractured seeds and interseminal scales still tightly packed together (e.g., fragment 17). Typically, these small fragments are broken at the base and only rarely are remains of the seed stalk preserved. One larger fragment (fragment 24) consists of several seeds with seed stalks intact. For comparison with Cycadeoidea morierei we also examined a fragment of another classic petrified seed cone, Cycadeoidea gibsoniana from the Early Cretaceous of isle of Wight, Southern England, using SRXTM. The results, combined with a comparative survey of other fossil material, indicate that the seeds of Bennettitales had at least one, perhaps two, envelopes covering the integument, comparable to what is seen among extant Gnetales, extinct Erdtmanithecales, and diverse fossil seeds recovered from Early Cretaceous mesofossil assemblages. Most of the SRXTM analyses of the Cycadeoidea material were carried during 2009-2023 on the TOMCAT beamline, SLS, Paul Scherrer Institute, Villigen, Switzerland. Fragment 24 was analysed at the new I-TOMCAT beamline at SLS in November 2025.

en: Synchrotron radiation X-ray tomographic microscopy datasets for seed structure in Cycadeoidea morierei

en: PSI Data Catalog


en:
This time-resolved tomographic microscopy dataset captures disintegration dynamics of pharmaceutical tablets. A diverse set of mini-tablets of 2 mm diameter with compositions varied according to a full factorial design of experiments were individually imaged as they underwent disintegration in water. We established a predominantly GPU based software pipeline for raw data reconstruction, including phase contrast filtering, and reconstructed image segmentation to enable visualization and quantitative analysis. The experimental system was highly dynamic, such that the quality of reconstructed images is impeded by motion artefacts, especially at advanced stages of tablet disintegration. To meet the challenges of varying image quality, we devised and trained a convolutional neural network (CNN) based on the U-Net architecture to segment the reconstructed images. Only the segmented data enables visualization for qualitative analysis and allows for quantification of the captured disintegration process.

Detailed descriptions of data acquisition parameters, the custom software pipeline used for image reconstruction and image segmentation, as well as a sample analysis of the data are discussed in the associated publicaton : https://doi.org/10.1016/j.heliyon.2024.e26025
The source code of the software pipeline used to reconstruct and segment the data is available here: https://github.com/walsam00/4D_CT_code
Videos visualizing the entire dataset are available here: https://zenodo.org/doi/10.5281/zenodo.7180040 as well as here:
https://www.youtube.com/watch?v=yESTXXv6wbM&list=PLPnSoY_iHSc410wtWpewTeFN3koH3gkQw&index=1

en: Three - dimensional reconstruction of time-resolved disintegration process in pharmaceutical tablets

en: The PSI Data Catalog is the central repository directory for scientific metadata generated at the Paul Scherrer Institut (PSI). Powered by SciCat—a community-driven, open-source metadata management framework co-developed by PSI—the catalog provides discoverability and standardized access pathways to petabyte-scale datasets produced across PSI’s large-scale research facilities, including the Swiss Light Source (SLS), the Swiss Spallation Neutron Source (SINQ), and the SwissFEL X-ray free-electron laser.


en:
The experimental realisation of unconventional superconductivity and charge order
in kagome systems AV3Sb5 is of critical importance. This work presents the most
systematic study to date, employing tuning parameters such as doping, hydrostatic
pressure, magnetic fields, and depth, using muon spin rotation, AC susceptibility, and
STM, to uncover tunable exotic magnetism in the normal state of Cs(V1−xNbx)3Sb5
with x=0.07 (Nb0.07-CVS), which transitions to a chiral superconducting state under
pressure. Our findings reveal that the bulk of Nb0.07-CVS (at depths >20 nm from the
surface) experiences time-reversal symmetry (TRS) breaking below T ∗ = 40 K, lower
than the charge order onset temperature, TCO = 58 K. However, near the surface (<20
nm), the TRS breaking signal doubles and onsets at TCO, indicating that Nb-doping
decouples TRS breaking from charge order in the bulk but synchronises them near
the surface. Additionally, Nb-doping raises the superconducting critical temperature
TC from 2.5 K to 4.4 K. Applying hydrostatic pressure enhances both TC and the
superfluid density by a factor of two, with a critical pressure pcr ≃ 0.85 GPa, suggesting
competition with charge order. Notably, above pcr, we observe nodeless electron pairing
and weak internal fields below TC, pointing to chiral superconducting pairing. Overall,
these results demonstrate a highly unconventional normal state with a tunable onset of
TRS breaking, and a transition to chiral superconductivity under low pressures, with
an unconventional correlation between TC and the superfluid density.

en: Pressure induced transition from chiral charge order to time-reversal symmetry-breaking superconducting state in Nb-doped CsV3Sb5 - LEM data

envi

en: Environment


en:
The articles based on this dataset discuss structural dynamics in an operating zero-gap forward-bias bipolar membrane CO2 electrolyzer using time-resolved X-ray tomographic microscopy. The employed setup provides high-quality four-dimensional imaging in a FOV of 5 mm height at 2.75 um voxel size and one full scan (1s acquisition) every minute. Different routes for segmentation yield the membrane with forming cavities, the catalyst layer and the porous cathode gas diffusion layer including pore and flow field filling with liquid water.
We find strong swelling of the membrane, membrane delamination, anode catalyst layer degradation, but no flooding of the cathode.

en: Operando X-ray tomography in bipolar membrane electrolyte CO2-electrolysis


en: This dataset has been used in the work titled ‘Metamorphic fabrics can be formed by stress without significant strain’ by Gilgannon et al. (2023). It was acquired at the TOMCAT beamline as part of a long term science proposal called ‘Implementing novel X-ray transparent triaxial deformation rigs to study fluid-rock interaction at mid-crustal conditions’. This research was funded through NERC standard grant NE/T001615/1.

en: Metamorphic fabrics can be formed by stress without significant strain - sample VA20


en: Metamorphic fabrics can be formed by stress without significant strain - sample VA18


en: Chloride transport by microbial rhodopsins is an essential process of which the molecular details have remained elusive, such as the mechanisms that convert light energy to drive ion pumping and ensure the unidirectionality of the transport. We combined time-resolved serial crystallography with time-resolved spectroscopy and multiscale simulations to elucidate the molecular mechanism of a chloride pumping rhodopsin and the structural dynamics throughout the transport cycle. We traced transient anion binding sites, obtained evidence for how light energy is used in the pumping mechanism, and identified steric and electrostatic molecular gates ensuring unidirectional transport. An interaction with the π-electron system of the retinal supports transient chloride ion binding across a major bottleneck in the transport pathway. These results allow us to propose key mechanistic features enabling finely controlled chloride transport across the cell membrane in this light powered chloride ion pump.

en: Dynamics and mechanism of a light-driven chloride pump - SFX datasets


en: Multiphase fluid flow through porous media occurs in various natural and engineered settings. How local wetting phenomena, such as those induced by pore-scale roughness, translate into effective multiphase fluid flow behavior observed at larger scales remains poorly understood. In this study, an unsteady-state waterflooding experiment in a sandstone sample with pronounced surface roughness was conducted and imaged using synchrotron-based sub-micron time-resolved X-ray tomography at the TOMCAT beamline of the Swiss Light Source. The data shows how local roughness features cause fluid displacements to occur as a series of smaller sub-pore scale events controlled by (de-)pinning of the fluid-fluid interface and wetting layer growth. Our data offers quantitative insights into multiphase fluid displacement process and provides a basis to verify numerical simulations of pore-scale multiphase fluid flow.

en: A submicron time-resolved X-ray tomography dataset investigating the role of surface roughness during multiphase flow in porous media


en: The ability of photofunctional organic molecules to perform chemical/mechanical work or convert photons into electrons results from a complex interplay between charge transfer and transient atomic rearrangements involving the local environment. These ultrafast structural dynamics have remained elusive experimentally, preventing a mechanistic understanding of the electronic-nuclear couplings. We will use the high X-ray photon flux and sub ps time resolution of the SwissFEL to realize the first X-ray scattering observation of solute-solvent dynamics following photoinduced charge transfer in an organic chromophore. The sensitivity of the scattering to changes in atomic distances will be exploited not only to track in real time the intra- and intermolecular structural dynamics but also to identify the electronic changes that trigger them. The results will pave the way for a better understanding of the factors governing the outcomes of photoreactions across chemistry and biology.

en: Photoinduced intramolecular and solvation dynamics of an organic chromophore in polar solvent


en: The small size, the location (embedded in the temporal bone), and the tiny movements of the three ossicles of the human middle ear make the study of sound transmission through the human auditory system extremely challenging. From the encouraging results of our previous investigations with dynamic synchrotron-based phase-contrast microtomography (proposal 20200954), we aim to further characterize the biomechanics of the human middle ear. The goal is to stimulate the middle ear with a broad range of sound frequencies, covering a wider spectrum of the human voice, together with a range of sound intensities meeting physiological criteria.

en: DYNAMITE: DYNamic phAse-contrast MIcro-Tomography of the human middle Ear

en: PSI Data Catalog


en: Low-energy muSR (LE-muSR) enables depth-resolved studies of magnetic and electronic properties from the surface into the near-surface region, but the measured transverse-field asymmetry is not an intrinsic constant but depends on implantation energy and beamline conditions. Following an upgrade of the single-muon tagging system at the LEM beamline at PSI in 2023, updated asymmetry calibrations are required. Here, we present updated reference measurements that establish the energy-dependent maximum asymmetry using a silver reference and quantify spurious contributions from reflected muons using a nickel reference. In addition, we address systematic reductions of the measured asymmetry arising from incomplete beam--sample overlap by introducing a sample-size-dependent correction factor. This factor is obtained from musrSim/Geant4 simulations incorporating an updated electrostatic field map of the sample environment and is benchmarked using implantation-energy scans on SrTiO3 samples of different dimensions. Together, these updated calibrations and the simulation-based overlap correction provide a practical and up-to-date framework for LE-muSR data correction under current beam conditions and enable quantitative depth-resolved analysis of (dia)magnetic volume fractions.

en: Correcting the Depth-Dependent Asymmetry in Low-Energy muSR

en: The PSI Data Catalog is the central repository directory for scientific metadata generated at the Paul Scherrer Institut (PSI). Powered by SciCat—a community-driven, open-source metadata management framework co-developed by PSI—the catalog provides discoverability and standardized access pathways to petabyte-scale datasets produced across PSI’s large-scale research facilities, including the Swiss Light Source (SLS), the Swiss Spallation Neutron Source (SINQ), and the SwissFEL X-ray free-electron laser.


en: Metamorphic fabrics can be formed by stress without significant strain - sample VA22

en: Environment


en: This dataset has been used in the work titled ‘Metamorphic fabrics can be formed by stress without significant strain’ by Gilgannon et al. (2023). It was acquired at the TOMCAT beamline as part of a long term science proposal called ‘Implementing novel X-ray transparent triaxial deformation rigs to study fluid-rock interaction at mid-crustal conditions’. This research was funded through NERC standard grant NE/T001615/1.

en: Metamorphic fabrics can be formed by stress without significant strain - sample VA_B


en: High-temperature and high-magnetic-field-induced re-entrant superconductivity has been discovered in the infinite-layer nickelate Sm1−x−yEuxCayNiO2 (SECNO). Infinite-layer nickelates are the closest known analogues of high-Tc cuprate superconductors, yet they host distinct magnetic ground states. Using low-energy muon spin relaxation and polarized neutron reflectometry, we reveal the magnetic order in SECNO. We find that magnetic freezing occurs at a higher-temperature than in other nickelate compounds, and that a substantial net magnetization of 55 kA m−1 ±10 kA m−1 emerges and remains largely unchanged across the superconducting transition. The magnetism in SECNO is disordered and nonuniform.

en: Net Magnetization and Inhomogeneous Magnetic Order in a High-Tc Nickelate Superconductor


en: The experiment aims at visualizing with high resolution stacking faults in InSb micropillars that were deformed in a microcompression experiment. The chosen method is ptychographic topography, a new method recently developed at the cSAXS beam line.

en: Visualization of stacking faults in InSb micropillars by ptychographic topography


barcodes-for-nanoporous-materials

en: In most applications of nanoporous materials the pore structure is as important as the chemical composition as a determinant of performance. For example, one can alter performance in applications like carbon capture or methane storage by orders of magnitude by only modifying the pore structure. For these applications it is therefore important to identify the optimal pore geometry and use this information to find similar materials. However, the mathematical language and tools to identify materials with similar pore structures, but different composition, has been lacking. Recently, we developed a pore recognition approach to quantify similarity of pore structures using topological data analysis. Barcodes generated with using this approach allow us to identify materials with similar pore geometries, and to screen for materials that are similar to given top-performing structures. This database has barcodes for zeolites, metal organic frameworks, and zeolitic imidazolate frameworks.

en: Barcodes for nanoporous materials

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).

en: Materials Cloud

de: Materials Cloud

fr: Materials Cloud

it: Materials Cloud

title_for_slug: barcodes-for-nanoporous-materials

value: DCAT Harvester Materials Cloud

marvel

display_name: marvel

metal-organic-frameworks

display_name: metal-organic-frameworks

nanoporous-materials

display_name: nanoporous-materials

persistence-homology

display_name: persistence-homology

topological-data-analysis

display_name: topological-data-analysis

zeolites

display_name: zeolites


en:
Project abstract: Frustrated magnets are one class of fascinating materials that host many intriguing phases such as spin ice, spin liquid and complex long-range magnetic orderings at low temperatures. In this work we use first-principles calculations to find that in a wide range of magnetically frustrated oxides, at zero temperature a number of non-collinear magnetic orderings are more stable than the type-I collinear ordering that is observed at finite temperatures. The emergence of non-collinear orderings in those complex oxides is due to higher-order exchange interactions that originate from second-row and third-row transition metal elements. This implies a collinear-to-noncollinear spin transition at sufficiently low temperatures in those frustrated complex oxides. Furthermore, we find that in a particular oxide Ba2YOsO6, experimentally feasible uniaxial strain can tune the material between two different non-collinear magnetic orderings. Our work predicts new non- collinear magnetic orderings in frustrated complex oxides at very low temperatures and provides a mechanical route to tuning complex non-collinear magnetic orderings in those materials.

About this entry:  We provide the input files of our DFT calculations for the studied complex oxides.  The structures in POSCAR format and the INCAR files for all stabilized magnetic orderings in our study are all included. These files can be directly used into DFT calculations with VASP.

en: The complex non-collinear magnetic orderings in Ba2YOsO6: A new approach to tuning spin-lattice interactions and controlling magnetic orderings in frustrated complex oxides

double-perovskite

display_name: double-perovskite

first-principles-calculations

display_name: first-principles-calculations

frustrated-complex-oxides

display_name: frustrated-complex-oxides

non-collinear-magnetic-ordering

display_name: non-collinear-magnetic-ordering

spin-orbital-coupling

display_name: spin-orbital-coupling


en: Canonical molecular dynamics simulations of crystal growth from solution suffer from severe finite-size effects. As the crystal grows, the solute molecules are drawn from the solution to the crystal, leading to a continuous drop in the solution concentration. This is in contrast to experiments in which the crystal grows at an approximately constant supersaturation of a bulk solution. Recently, Perego et al. [J. Chem. Phys.2015, 142, 144113] showed that in a periodic setup in which the crystal is represented as a slab, the concentration in the vicinity of the two surfaces can be kept constant while the molecules are drawn from a part of the solution that acts as a molecular reservoir. This method is quite effective in studying crystallization under controlled supersaturation conditions. However, once the reservoir is depleted, the constant supersaturation conditions cannot be maintained. We propose a variant of this method to tackle this depletion problem by simultaneously dissolving one side of the crystal while letting the other side grow. A continuous supply of particles to the solution due to the crystal dissolution maintains a steady solution concentration and avoids reservoir depletion. In this way, a constant supersaturation condition can be maintained for as long as necessary. We have applied this method to study the growth and dissolution of urea crystal from water solution under constant supersaturation and undersaturation conditions, respectively. The computed growth and dissolution rates are in good agreement with those obtained in previous studies.

en: A Cannibalistic Approach to Grand Canonical Crystal Growth

crystal-nucleation-and-growth

display_name: crystal-nucleation-and-growth

erc

display_name: erc

solution-crystallization

display_name: solution-crystallization


en:
We present a workflow that traces the path from the bulk structure of a crystalline material to assessing its performance in carbon capture from coal's postcombustion flue gases. This workflow is applied to a database of 324 covalent−organic frameworks (COFs) reported in the literature, to characterize their CO2 adsorption properties using the following steps:
(1) optimization of the crystal structure (atomic positions and unit cell) using density functional theory,
(2) fitting atomic point charges based on the electron density,
(3) characterizing the pore geometry of the structures before and after optimization,
(4) computing carbon dioxide and nitrogen isotherms using grand canonical Monte Carlo simulations with an empirical interaction potential, and finally,
(5) assessing the CO2 parasitic energy via process modeling.

The full workflow has been encoded in the Automated Interactive Infrastructure and Database for Computational Science (AiiDA). Both the workflow and the automatically generated provenance graph of our calculations are made available on the Materials Cloud, allowing peers to inspect every input parameter and result along the workflow, download structures and files at intermediate stages, and start their research right from where this work has left off. In particular, our set of CURATED (Clean, Uniform, and Refined with Automatic Tracking from Experimental Database) COFs, having optimized geometry and high-quality DFT-derived point charges, are available for further investigations of gas adsorption properties. We plan to update the database as new COFs are being reported.

*** UPDATE December 2019 ***
 - Database extended to  include 417 COFs (from papers published until September 1st 2019)
- Migration to AiiDA-v1.0.0
- Using the publicly available plugin aiida-lsmo

*** UPDATE February 2020 ***
 - Database extended to  include 505 COFs (from papers published until February 1st 2020)
 - Including AiiDA Groups for quick interactive visualization

*** UPDATE June 2020 ***
 - Database extended to include 574 COFs (from papers published until June 1st 2020)

*** UPDATE September 2020 ***
 - Include other applications than CCS, considering the same set of 574 COFs

*** UPDATE October 2020 ***
 - Database extended to include 626 COFs (from papers published until October 1st 2020)

*** UPDATE February 2021 ***
 - Database extended to include 632 COFs (from papers published until February 1st 2021). We added a total of 61 new structures but we discarded 55: see CURATED-COFs GitHub for more details.

*** UPDATE June 2021 ***
 - Database extended to include 648 valid COFs (from papers published until June 1st 2021) plus 80 discarded: see CURATED-COFs GitHub for more details.

*** UPDATE July 2022 ***
 - Database extended to include 871 valid COFs (from papers published until July 1st 2022) plus 110 discarded: see CURATED-COFs GitHub for more details.

en: Building a consistent and reproducible database for adsorption evaluation in Covalent-Organic Frameworks

aiida

display_name: aiida

covalent-organic-framework

display_name: covalent-organic-framework

marvelosp

display_name: marvelosp

reproducibility

display_name: reproducibility

workflows

display_name: workflows


en: This record mainly upload all the raw experimental data related to the manuscript. Fig1 include the transport data, magnetotransport data, AHE data, ESR data, uSR data. These data related to the conclusion that spin fluctuation established in the paramagnetic phase. Fig2 contains in-plane and out-of-plane 3D photoemission spectra, and high resolution cuts on top and side surface. Fig3 contains band electronic structure along high symmetry lines with spin along all kinds of typical directions. Fig4 contains 3-D in-plane and out-of-plane Fermi surfaces on the 101 cleavage, high resolution cuts, STM/STS data. The proved the observation of Weyl points.

en: Spin fluctuation induced Weyl semimetal state in the paramagnetic phase of EuCd2As2

envi

en: Environment

arpes

display_name: arpes

magnetic-material

display_name: magnetic-material

magnetic-weyl-semimetal

display_name: magnetic-weyl-semimetal

spin-fluctuation

display_name: spin-fluctuation

topological-material

display_name: topological-material


en: Interatomic potentials are often necessary to describe complex realistic systems that would be too costly to study from first-principles. Commonly, interatomic potentials are designed using functional forms driven by physical intuition and fitted to experimental or computational data. The moderate flexibility of these functional forms limits their ability to be systematically improved by increasing the fitting datasets; on the other hand, their qualitative description of the essential physical interactions ensures a modicum degree of transferability. Recently, a novel trend has emerged where potential-energy surfaces are represented by neural networks fitted on large numbers of first-principles calculations, thus maximizing flexibility but requiring extensive datasets to ensure transferability. Gaussian Approximation Potentials in particular are a novel class of potentials based on non-linear, non-parametric Gaussian-process regression. Here we generate a Gaussian Approximation model for the α-phase of iron training on energies, stresses and forces taken from first-principles molecular dynamics simulations of pristine and defected bulk systems, of surfaces and γ-surfaces with different crystallographic orientations.

en: Gaussian Approximation Potentials for iron from extended first-principles database (Data Download)

artificial-neural-networks

display_name: artificial-neural-networks

gaussian-approximation-potentials

display_name: gaussian-approximation-potentials

interatomic-potentials

display_name: interatomic-potentials

iron

display_name: iron

machine-learning

display_name: machine-learning

marvel

display_name: marvel


en: We study the oxo-hexametallate Li7TaO6 with first-principles and classical molecular dynamics simulations, obtaining a low activation barrier for diffusion of ∼0.29 eV and a high ionic conductivity of 5.7×10−4 S cm−1 at room temperature (300 K). We find evidence for a wide electrochemical stability window from both calculations and experiments, suggesting its viable use as a solid-state electrolyte in next-generation solid-state Li-ion batteries. To assess its applicability in an electrochemical energy storage system, we performed electrochemical impedance spectroscopy measurements on multicrystalline pellets, finding substantial ionic conductivity, if below the values predicted from simulation. We further elucidate the relationship between synthesis conditions and the observed ionic conductivity using X-ray diffraction, inductively coupled plasma optical emission spectrometry, and X-ray photoelectron spectroscopy, and study the effects of Zr and Mo doping.

en: The solid-state Li-ion conductor Li7TaO6: A combined computational and experimental study

big-map

display_name: big-map

density-functional-theory

display_name: density-functional-theory

electrochemical-stability

display_name: electrochemical-stability

li-ion-batteries

display_name: li-ion-batteries

molecular-dynamics

display_name: molecular-dynamics

polarizable-force-fields

display_name: polarizable-force-fields

solid-state-electrolyte

display_name: solid-state-electrolyte


en: Multiple mechanisms for extremely large magnetoresistance (XMR) found in many topologically nontrivial/trivial semimetals have been theoretically proposed, but experimentally it is unclear which mechanism is responsible in a particular sample. In this paper, by the combination of band structure calculations, numerical simulations of magnetoresistance (MR), Hall resistivity, and de Haas-van Alphen (dHvA) oscillation measurements, we studied the MR anisotropy of SiP2 which is verified to be a topologically trivial, incomplete compensation semimetal. It was found that as magnetic field H is applied along the a-axis, the MR exhibits an unsaturated nearly linear H dependence, which was argued to arise from incomplete carriers compensation. For the H // [101] orientation, an unsaturated nearly quadratic H dependence of MR up to 5.88 × 10^4%(at 1.8 K, 31.2 T) and field-induced up-turn behavior in resistivity were observed, which was suggested due to the existence of hole open orbits extending along the kx direction. Good agreement of the experimental results with the simulations based on the calculated Fermi surface (FS) indicates that the topology of FS plays an important role in its MR.

en: Linear and quadratic magnetoresistance in the semimetal SiP2

cscs

display_name: cscs

epfl

display_name: epfl

magnetoresistance

display_name: magnetoresistance

wanniertools

display_name: wanniertools


en: Donor–acceptor (D–A) copolymers have shown great potential for intramolecular singlet fission (iSF). Nonetheless, very few design principles exist for optimizing these systems for iSF, with very little knowledge about how to engineer them for this purpose. In recent work, a fundamental trade-off between the main electronic ingredients required for iSF capable D–A coplanar copolymers was revealed. Still, further investigations are needed to understand these limitations and learn how to bypass them. In this work, we propose to induce torsion as an effective way to circumvent the limits of the coplanar approach. We disclose the potential of noncoplanar copolymers with inherently low triplet energies that encompass all the characteristics required for iSF beyond the limiting values associated with fully coplanar systems. Our findings shed some light on the electronic structure aspects of D–A copolymers for iSF and offer a new avenue for the rational design of novel promising candidates.

en: Pushing the limits of the donor-acceptor copolymer strategy for intramolecular singlet fission

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

electronic-structure

display_name: electronic-structure

marie-curie-fellowship

display_name: marie-curie-fellowship

singlet-fission

display_name: singlet-fission


en: Detection of electromagnetic signals for applications such as health, product quality monitoring or astronomy requires highly responsive and wavelength selective devices. Photomultiplication-type organic detectors (PM-OPDs) have shown to achieve high quantum efficiencies mainly in the visible range. Much less research has been focused on realizing near-infrared narrowband PM-OPDs. Here, we demonstrate fully vacuum-processed narrow- and broadband PM‑OPDs. Our devices are based on enhanced hole injection leading to a maximum external quantum efficiency (EQE) of almost 2000% at -10 V for the broadband device. The photomultiplicative effect is also observed in the charge-transfer (CT) state absorption region. By making use of an optical cavity device architecture, we enhance CT absorption and demonstrate a wavelength tunable narrowband PM-OPD with EQEs superior to those of pin‑devices. The presented concept can further improve the performance of state-of-the-art OPDs based on the absorption of CT states, which were so far limited by the low EQE provided by these devices.

en: Enhancing sub-bandgap external quantum efficiency by photomultiplication for narrowband organic near-infrared photodetectors

materialscloud

en: Materials Cloud

experimental

display_name: experimental

narrowband

display_name: narrowband

organic-photodetectors

display_name: organic-photodetectors

photomultiplication

display_name: photomultiplication


en: We investigate twisted double bilayer graphene (TDBG), a four-layer system composed of two AB-stacked graphene bilayers rotated with respect to each other by a small angle. Our ab-initio band structure calculations reveal a considerable energy gap at the charge point neutrality that we assign to the intrinsic symmetric polarization (ISP). We then introduce the ISP effect into the tight-binding parameterization and perform calculations on TDBG models that include lattice relaxation effects down to very small twist angles. We identify a narrow region around the magic angle θ*= 1.3° characterized by a manifold of remarkably flat bands gapped out from other states even without external electric fields. To understand the fundamental origin of the magic angle in TDBG, we construct a continuum model that points to a hidden mathematical link to the twisted bilayer graphene (TBG) model, thus indicating that the band flattening is a fundamental feature of TDBG, and is not a result of external fields.

en: Moiré Flat Bands in Twisted Double Bilayer Graphene

continuum-model

display_name: continuum-model

flat-bands

display_name: flat-bands

magic-angle

display_name: magic-angle

moire-superlattice

display_name: moire-superlattice

snsf

display_name: snsf

tight-binding-model

display_name: tight-binding-model

twisted-double-bilayer-graphene

display_name: twisted-double-bilayer-graphene


en:
Regioselective derivatization of oligosaccharides is a challenging issue in carbohydrate chemistry. A commonly required series of (de)protection steps substantially lowers synthetic yields and increases time demands. We present here a regioselective one-step introduction of benzylic substituents at 3-hydroxy moieties of beta-D-galactopyranosyl-(1<->1)-thio-beta-D-galactopyranoside (TDG) employing tin butyl oxide in fair isolated yields. These glycomimetics act as inhibitors of galectins - human lectins, which are biomedically attractive targets for therapeutic inhibition. The affinity of prepared glycomimetics to recombinant galectin-1 and galectin-3 was studied in ELISA-type assay and their inhibitory potential was also demonstrated on the surface of a model HEK293 cell line. The results of biological experiments were correlated with data from molecular modelling with both galectins. The present work reveals a facile and elegant synthetic route for the preparation of glycomimetics that exhibit differing selectivity and affinity to various galectins depending on the choice of 3-O-substitution.
In order to rationalize structure-activity relationships of tested ligands we carried out a series of molecular dynamics simulations and quantum chemical calculations. We present input and output files for quantum chemical geometry optimizations and calculations of interactions energies. These calculations were carried out in Gaussian 09 package. These results can be visualized using Molden, Molekel or other programs.
Molecular dynamics simulations were carried out using Gromacs 5.1.3 package. Initial structures of production simulations and trajectories (without water) are presented. The results can be visualized by VMD or other structure visualization packages with a support for trajectory input.

en: Regioselective 3-O-Substitution of Unprotected Thiodigalactosides: Direct Route to Galectin Inhibitors

galectin

display_name: galectin

glycobiology

display_name: glycobiology

molecular-dynamics-simulation

display_name: molecular-dynamics-simulation


en: We present a fully ab-initio, unbiased structure search of the configurational space of decorated C60 fullerenes in the presence of an electric field. We observed that the potential energy surface (PES) is significantly perturbed by an external electric field and that the energetic ordering of low energy isomers differs with and without electric field. We identify the energetically lowest configuration for a varying number of decorating atoms (1 ≤ n ≤ 12) for Li and (1 ≤ n ≤ 6) for K on the C60 surface at different electric field strengths. Using the correct geometric ground state in the electric field for the calculation of the dipole we obtain better agreement with the experimentally measured values than previous calculations based on the ground state in absence of an electric field. Since the lowest energy structures are typically nearly degenerate in energy, a combination of different structures is expected to be found at room temperature. The experimentally measured dipole is therefore also expected to contain significant contributions from several low energy structures.

en: Influence of an external electric field on the potential energy surface of alkali decorated C60

envi

en: Environment

alkali-atom

display_name: alkali-atom

electric-field

display_name: electric-field

free-energy

display_name: free-energy


en: Ultrafast electron delocalization induced by a femtosecond laser pulse is a well-known process in which electrons are ejected from the ions within the laser pulse duration. However, very little is known about the speed of electron localization out of an electron gas in correlated metals, i.e., the capture of an electron by an ion. Here, we demonstrate by means of pump-probe x-ray techniques across the Eu L3 absorption edge that an electron localization process in the EuNi2(Si0.21Ge0.79)2 intermetallic material occurs within a few hundred femtoseconds after the optical excitation. Spectroscopy and diffraction data collected simultaneously at low temperature and for various laser fluences show that the localization dynamics process is much faster than the thermal expansion of the unit cell along the c direction which occurs within picoseconds. Nevertheless, this latter process is still much slower than pure electronic effects, such as screening, and the subpicosecond timescale indicates an optical phonon drive origin. In addition, comparing the laser fluence dependence of the electronic response with that found in other intermediate 4 f valence materials, we suggest that the electron localization process observed in this Eu-based correlated metal is mainly related to changes in the 4 f hybridization. The observed ultrafast electron localization process sparks fundamental questions for our understanding of electron correlations and their coupling to the lattice.

en: Ultrafast electron localization in the EuNi2(Si0.21Ge0.79)2 correlated metal

experimental

display_name: experimental

pump-and-probe-x-ray-techniques

display_name: pump-and-probe-x-ray-techniques

ultrafast-electron-delocalization

display_name: ultrafast-electron-delocalization

valence-transition

display_name: valence-transition


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

en: Yttrium tantalum oxynitride multiphases as photoanodes for water oxidation

computational-screening

display_name: computational-screening

marvel

display_name: marvel

oxynitride-perovskite

display_name: oxynitride-perovskite

solar-water-splitting

display_name: solar-water-splitting


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

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

dftuv

display_name: dftuv

oxygen-vacancies

display_name: oxygen-vacancies

prace

display_name: prace

snsf

display_name: snsf


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

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

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).

delocalization-error

display_name: delocalization-error

density-functional-theory

display_name: density-functional-theory

epfl

display_name: epfl

london-dispersion-interactions

display_name: london-dispersion-interactions

organic-semiconductors

display_name: organic-semiconductors

radical-cation-dimers

display_name: radical-cation-dimers


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

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

materialscloud

en: Materials Cloud

mof

display_name: mof

photocatalysis

display_name: photocatalysis

screening

display_name: screening


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

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

ab-initio

display_name: ab-initio

effective-hamiltonians

display_name: effective-hamiltonians

erc

display_name: erc

hidden-order

display_name: hidden-order

linear-response

display_name: linear-response

strongly-correlated-electrons

display_name: strongly-correlated-electrons


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

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

big-map

display_name: big-map

molecular-dynamics

display_name: molecular-dynamics

site-analysis

display_name: site-analysis

tracer-diffusion

display_name: tracer-diffusion


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

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

envi

en: Environment

dmft

display_name: dmft

first-principles

display_name: first-principles

transition-metal-dichalcogenides

display_name: transition-metal-dichalcogenides


en: This record contains the first experimental results obtained at the time-resolved ARPES endstation developed at the Lausanne Centre for Ultrafast Science. The use of VUV photons, generated by means of high-harmonic generation in gas, allows us to explore the out-of-equilibrium electron dynamics over the entire Brillouin zone of solids. In this work we give evidence of this capability by accessing the linearly dispersing surface state of the nodal-line Dirac semimetal ZrSiTe.

en: Time-resolved ARPES at LACUS: band structure and ultrafast electron dynamics of solids

electronic-bands

display_name: electronic-bands

experimental

display_name: experimental

nodal-line-dirac-semimetal

display_name: nodal-line-dirac-semimetal

snsf

display_name: snsf

ultrafast-electronic-spectroscopy

display_name: ultrafast-electronic-spectroscopy


en: We perform a systematic ab initio study of the electronic structure of Sr(V,Mo,Mn)O3 perovskites, using the parameter-free GW+EDMFT method. This approach self-consistently calculates effective interaction parameters, taking into account screening effects due to nonlocal charge fluctuations. Comparing the results of a 3-band (t2g) description to those of a  5-band (t2g+eg) model, it is shown that the eg states have little effect on the low-energy properties and the plasmonic features for the first two compounds but play a more active role in SrMnO3. In the case of SrMnO3 paramagnetic GW+EDMFT yields a metallic low-temperature solution on the verge of a Mott transition, while antiferromagnetic GW+EDMFT produces an insulating solution with the correct gap size. We discuss the possible implications of this result for the nature of the insulating state above the Neel temperature, and the reliability of the GW+EDMFT scheme.

en: Screening from eg states and antiferromagnetic correlations in d(1,2,3) perovskites: A GW+EDMFT investigation

correlated-oxides

display_name: correlated-oxides

dynamical-mean-field-theory

display_name: dynamical-mean-field-theory

gwedmft

display_name: gwedmft


en: CO is the simplest product from CO2 electroreduction (CO2R), but the identity and nature of its rate limiting step remains controversial. Here we investigate the activity of both transition metals (TMs) and metal-nitrogen doped carbon catalysts (MNCs), and a present unified mechanistic picture of CO2R for both these classes of catalysts. By consideration of the electronic structure through a Newns-Andersen model, we find that on MNCs, like TMs, electron transfer to CO2 is facile, such that CO2 (g) adsorption is driven by adsorbate dipole-field interactions. Using density functional theory with explicit consideration of the interfacial field, we find CO2 * adsorption to generally be limiting on TMs, while MNCs can be limited by either CO2* adsorption or by the proton-electron transfer reaction to form COOH*. We evaluate these computed mechanisms against pH-dependent experimental activity measurements on CO2R to CO activity for Au, FeNC, and NiNC. We present a unified activity volcano that, in contrast to previous analyses, includes the decisive CO2* and COOH* binding strengths as well as the critical adsorbate dipole-field interactions. This dataset contains all DFT calculations used in this work.

en: Unified mechanistic understanding of CO2 reduction to CO on transition metal and single atom catalysts

catalysis

display_name: catalysis

dipole-field

display_name: dipole-field

electrocataylsis

display_name: electrocataylsis


en: We elucidate the nature of the electron-phonon interaction in the archetypal hybrid perovskite CH₃NH₃PbI₃ using ab initio many-body calculations and an exactly solvable model. We demonstrate that electrons and holes near the band edges primarily interact with three distinct groups of longitudinal-optical vibrations, in order of importance: the stretching of the Pb-I bond, the bending of the Pb-I-Pb bonds, and the libration of the organic cations. These polar phonons induce ultrafast intraband carrier relaxation over timescales of 6–30 fs and yield polaron effective masses 28% heavier than the bare band masses. These findings allow us to rationalize previous experimental observations and provide a key to understanding carrier dynamics in halide perovskites.

en: Carrier lifetimes and polaronic mass enhancement in the hybrid halide perovskite CH₃NH₃PbI₃ from multiphonon Fröhlich coupling

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).

electron-phonon-coupling

display_name: electron-phonon-coupling

first-principles-calculations

display_name: first-principles-calculations

perovskite

display_name: perovskite

prace

display_name: prace

semiconductors

display_name: semiconductors


en: Blending organic molecules to tune their energy levels is currently investigated as an approach to engineer the bulk and interfacial optoelectronic properties of organic semiconductors. It has been proven that the ionization energy (IE) and electron affinity (EA) can be equally shifted in the same direction by electrostatic effects controlled by blending similar halogenated derivatives with different energetics. Here, we show that the energy gap of organic semiconductors can be tuned by blending as well. We use oligothiophenes with different numbers of thiophene rings as example and investigate their structure and electronic properties. Photoelectron spectroscopy and inverse photoelectron spectroscopy show tunability of the single-particle gap, with the optical gaps showing similar, but smaller effects. Theoretical analysis shows that this tuning is mainly caused by a change in the dielectric constant with blend ratio. Further studies will explore the practical impact of this energy-level engineering strategy in optoelectronic devices.

en: Band gap engineering in blended organic semiconductor films based on dielectric interactions

materialscloud

en: Materials Cloud

dielectric-interactions

display_name: dielectric-interactions

energy-level-tuning

display_name: energy-level-tuning

photoelectron-spectroscopy

display_name: photoelectron-spectroscopy

theoretical-simulations

display_name: theoretical-simulations


en: Hundreds of catalytic methods are developed each year to meet the demand for high-purity chiral compounds. The computational design of enantioselective organocatalysts remains a significant challenge, as catalysts are typically discovered through experimental screening. Recent advances in combining quantum chemical computations and machine learning (ML) hold great potential to propel the next leap forward in asymmetric catalysis. Within the context of quantum chemical machine learning (QML, or atomistic ML), the ML representations used to encode the structure of molecules and evaluate their similarity cannot easily capture the subtle energy differences that govern enantioselectivity. Here, we present a general strategy for improving molecular representations within an atomistic machine learning model to predict the enantiomeric excess of asymmetric propargylation organocatalysts solely from the structure of catalytic cycle intermediates. Mean absolute errors as low as 0.25 kcal mol-1 were achieved in predictions of the activation energy. This strategy opens the door for quickly and accurately predicting higher-selectivity catalysts for any reaction from available structural information.

en: Reaction-based machine learning representations for predicting the enantioselectivity of organocatalysts

enantioselectivity

display_name: enantioselectivity

machine-learning

display_name: machine-learning

marvel

display_name: marvel

organocatalyst

display_name: organocatalyst


en: Amorphous alumina (a-AlOx), which plays important roles in several technological fields, shows wide variation of the density and composition. However, their influences on the properties of a-AlOx have rarely been investigated from a theoretical perspective. In this study, high dimensional neural network (NN) potentials were constructed to generate a series of atomic structures of a-AlOx with different densities (2.6–3.3 g/cm3) and O/Al ratios (1.0–1.75). The structural, vibrational, mechanical, and thermal properties of the a-AlOx models were investigated, as well as the Li and Cu diffusion behaviour in the models. The results showed that the density and composition had different degrees of effects on the different properties. The structural and vibrational properties were strongly affected by the composition, whereas the mechanical properties were mainly determined by the density. The thermal conductivity was affected by both the density and composition of a-AlOx. However, the effects on the Li and Cu diffusion behaviour were relatively unclear.

en: Effects of the density and composition on the properties of amorphous alumina: a high dimensional neural network potential study

aluminum-oxide

display_name: aluminum-oxide

amorphous

display_name: amorphous

neural-network-potential

display_name: neural-network-potential


en: In this paper we use density functional theory combined with dynamical mean-field theory (DFT+DMFT) to study interface effects between the correlated metal CaVO3 and the two typical substrate materials SrTiO3 and LaAlO3. We find that the CaVO3/SrTiO3 interface has only a marginal influence on the CaVO3 thin film, with the dominant effect being the (bulklike) epitaxial strain imposed by the large lattice mismatch, rendering the CaVO3 film insulating due to the enhanced orbital polarization related to the strong level splitting between the t2g orbitals. In contrast, at the polar CaVO3/LaAlO3 interface, the presence of the interface can have a huge effect on the physical properties, depending both on the specific interface termination and on the specific boundary conditions imposed by the multilayer geometry. We compare three approaches to modeling the CaVO3/LaAlO3 interface, all of which impose a different set of (electrostatic) boundary conditions. Our results demonstrate that different substrates, interface terminations, and electrostatic boundary conditions can drastically affect the properties of thin-film heterostructures, indicating the potential tunability of the interfacial properties via multilayer engineering.

en: Tailoring interfacial properties in CaVO3 thin films and heterostructures with SrTiO3 and LaAlO3: A DFT+DMFT study

envi

en: Environment

correlated-metal

display_name: correlated-metal

dynamical-mean-field-theory

display_name: dynamical-mean-field-theory

metal-insulator-transition

display_name: metal-insulator-transition

multilayer-thin-films

display_name: multilayer-thin-films

superlattices

display_name: superlattices


en: Photoelectrochemical solar water splitting is a promising approach to convert solar energy into sustainable hydrogen fuel using semiconductor electrodes. Due to their visible light absorption properties, oxynitrides have shown to be attractive photocatalysts for this application. In this study, the influence of the preparation method of CaNbO2N particles on their morphological and optical properties, and thereby their photoelectrochemical performance, is investigated. The best performing CaNbO2N photoanode is produced by ammonolysis of Nb enriched calcium niobium oxide. The enhanced photoactivity arises from an enlarged surface area and superior visible light absorption properties. The photoactivity of this photoanode was further enhanced by photodeposition of Co-Pi co-catalyst and by atomic layer deposition of an Al2O3 overlayer. A photocurrent density of 70 mA at 1.23 V vs RHE was achieved. The observed enhancement of the photoelectrochemical performance after Co-Pi/Al2O3 deposition is the combined effect of the improved kinetics of oxygen evolution due to the Co-Pi co-catalyst and the reduced surface recombination of the photogenerated carriers at the Al2O3 surface layer.

en: Improved photoelectrochemical water splitting of CaNbO2N photoanodes by Co-Pi photodeposition and surface passivation

computational-screening

display_name: computational-screening

photoelectrochemical-water-splitting

display_name: photoelectrochemical-water-splitting

surface-passivation

display_name: surface-passivation


en: Temperature-induced Lifshitz transitions have been identified in several materials. Their chemical potential shows a substantial shift with changing temperature. The common feature of these materials is the coexistence of electron and hole pockets in the vicinity of the chemical potential. Here, we report the observation of temperature-induced chemical potential shift and Lifshitz transition in a layered type-II Weyl semimetal, TaIrTe4. The reversal of the polarity of the Hall resistivity and thermoelectric power (TEP) as the temperature increases clearly signal an appreciable shift of the chemical potential and change of the Fermi surface. It is corroborated by the improving agreement between the experimental TEP and the one calculated with temperature-dependent chemical potential. The complete disappearance of an electron pocket, consistent with the change of the Fermi surface when the chemical potential moves downwards, provides an evident signature of a temperature-induced Lifshitz transition in TaIrTe4.

en: Transport signatures of temperature-induced chemical potential shift and Lifshitz transition in layered type-II Weyl semimetal TaIrTe4

chemical-potential-shift

display_name: chemical-potential-shift

cscs

display_name: cscs

epfl

display_name: epfl

lifshitz-transition

display_name: lifshitz-transition

thermoelectric-power

display_name: thermoelectric-power

two-channel-model

display_name: two-channel-model

weyl-semimetal

display_name: weyl-semimetal


en:
Folding of villin miniprotein was studied by parallel tempering metadynamics driven by machine learning. To obtain a training set for machine learning, we generated a large series of structures of the protein by the de novo protein structure prediction package Rosetta. A neural network was trained to approximate the Rosetta score. Parallel tempering metadynamics driven by this approximated Rosetta score successfully predicted the native structure and the free energy surface of the studied system.
These files make it possible to rerun all simulations. The directory METAD contains input files for metadynamics (no folding events observed). The directory PT-METAD contains input files for parallel tempering metadynamics. All simulations were done using Gromacs 2016.4, Anncolvar 0.8, Plumed 2.4 and OpenMPI 4.0.0.

en: Sampling enhancement by metadynamics driven by machine learning and de novo protein modelling

collective-variable

display_name: collective-variable

machine-learning

display_name: machine-learning

metadynamics

display_name: metadynamics

protein-folding

display_name: protein-folding

scoring-function

display_name: scoring-function


en: Cif files of relaxed "derived" copper surfaces from Cu2O, Cu2S, Cu3N, and Cu3P using EMT and published in J Gauthier, JH Stenlid, F Abild-Pedersen, M Head-Gordon, AT Bell, ACS Energy Letters, "The role of roughening to enhance selectivity to C2+ products during CO2 electroreduction on copper" (2021). These structures were used to evaluate the effect of roughening on catalytic selectivity of copper in electrochemcial CO2 reduction into valuable products such as fuels and commodity chemicals.

en: Atomic structures of 100nm x 100nm large oxide-, nitride-, sulfide-, and phosphide-derived copper surfaces

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).

atomic-coordinates

display_name: atomic-coordinates

copper

display_name: copper

surface-structure

display_name: surface-structure


en:
One proposed mechanism of implant fouling is attributed to the nonspecific adsorption of non-collagenous bone matrix proteins (NCPs) onto a newly implanted interface. With the goal of capturing the fundamental mechanistic and thermodynamic forces that govern changes in these NCP recognition domains as a function of γ-carboxyglutamic acid (Gla) post-translational modification and surface chemistry, we probe the adsorption process of the most commonly occurring NCP, osteocalcin, onto a mineral and metal oxide surface. Here, we apply two enhanced sampling methods to independently probe the effects of post-translational modification and peptide structure on adsorption. First, well-tempered metadynamics was used to capture the binding of acetyl and N-methylamide capped glutamic acid and Gla single amino acids onto crystalline hydroxyapatite and titania model surfaces at physiological pH. Following this, parallel tempering metadynamics in the well-tempered ensemble (PTMetaD-WTE) was used to study adsorption of the α-1 domain of osteocalcin onto hydroxyapatite and titania. Simulations were performed for the α-1 domain of osteocalcin in both its fully decarboxylated (dOC) and fully carboxylated (OC) form. Our simulations find that increased charge density due to carboxylation results in increased interactions at the interface, and stronger adsorption of the single amino acids to both surfaces. Interestingly, the role of Gla in promoting compact and helical structure in the α-1 domain resulted in disparate binding modes at the two surfaces, which is attributed to differences in interfacial water behavior. Overall, this work provides a benchmark for understanding the mechanisms that drive adsorption of Gla-containing mineralizing proteins onto different surface chemistries.

This record contains files necessary to reproduce enhanced sampling well-tempered metadynamics (wtMTD) and parallel tempering metadynamics in the well-tempered ensemble (PT-MetaD-WTE) simulations in PLUMED using GROMACS 2018.3.

en: Impact of glutamate carboxylation in the adsorption of the alpha-1 domain of osteocalcin to hydroxyapatite and titania

materialscloud

en: Materials Cloud

biomimetics

display_name: biomimetics

biomineralization

display_name: biomineralization

molecular-dynamics

display_name: molecular-dynamics


en: Density-functional theory is widely used to predict the physical properties of materials. However, it usually fails for strongly correlated materials. A popular solution is to use the Hubbard corrections to treat strongly correlated electronic states. Unfortunately, the exact values of the Hubbard U and J parameters are initially unknown, and they can vary from one material to another. In this semi-empirical study, we explore the U and J parameter space of a group of iron-based compounds to simultaneously improve the prediction of physical properties (volume, magnetic moment, and bandgap). We used a Bayesian calibration assisted by Markov chain Monte Carlo sampling for three different exchange-correlation functionals (LDA, PBE, and PBEsol). We found that LDA requires the largest U correction. PBE has the smallest standard deviation and its U and J parameters are the most transferable to other iron-based compounds. Lastly, PBE predicts lattice parameters reasonably well without the Hubbard correction.

en: Exploring DFT+U parameter space with a Bayesian calibration assisted by Markov chain Monte Carlo sampling

bayesian-calibration

display_name: bayesian-calibration

dftu

display_name: dftu

markov-chain-monte-carlo

display_name: markov-chain-monte-carlo

mcmc

display_name: mcmc


en: In this record we provide data to support our recent findings for the fabrication of Unsaturated Carbon Nanostructures with Regularly Fused Pentagon–Heptagon Pairs. Multiple fused pentagon–heptagon pairs are frequently found as defects at the grain boundaries of the hexagonal graphene lattice and are suggested to have a fundamental influence on graphene-related materials. However, the construction of sp2-carbon skeletons with multiple regularly fused pentagon–heptagon pairs is challenging. In this work, we found that the pentagon–heptagon skeleton of azulene was rearranged during the thermal reaction of an azulene-incorporated organometallic polymer on Au(111). The resulting sp2-carbon frameworks were characterized by high-resolution scanning probe microscopy techniques and feature novel polycyclic architectures composed of multiple regularly fused pentagon–heptagon pairs. Moreover, the calculated analysis of its aromaticity revealed a peculiar polar electronic structure.

en: On-surface synthesis of unsaturated carbon nanostructures with regularly fused pentagon-heptagon pairs

carbon-nanostructures

display_name: carbon-nanostructures

cscs

display_name: cscs

on-surface-synthesis

display_name: on-surface-synthesis

open-shell-systems

display_name: open-shell-systems

polymers

display_name: polymers

snsf

display_name: snsf


en: The paper reports on a theoretical description of work function of TiN, which is one of the most used materials for the realization of electrodes and gates in CMOS devices. Indeed, although the work function is a fundamental quantity in quantum mechanics and also in device physics, as it allows the understanding of band alignment at heterostructures and gap states formation at the metal/semiconductor interface, the role of defects and contaminants is rarely taken into account. Here, by using first principles simulations, we present an extensive study of the work function dependence on nitrogen vacancies and surface oxidation for different TiN surface orientations. The results complement and explain a number of existent experimental data, and provide a useful tool to tailoring transport properties of TiN electrodes in device simulations.

en: Controlling the TiN electrode work function at the atomistic level: a first principles investigation

envi

en: Environment

defects

display_name: defects

dft

display_name: dft

electrodes

display_name: electrodes

gates

display_name: gates

intersect

display_name: intersect

oxidation

display_name: oxidation

titanium-nitride

display_name: titanium-nitride


en: The dataset contains the result of 48 Nudged Elastic Band calculations of Li(2-x)VO2F diffusion barriers in the format of Atomic Simulation Environment (ASE) trajectories. The NEB was performed with VASP, using projector augmented-wave (PAW) method to describe electron-ion interaction. The disordered rock salt cells were created using a 3 x 4 x 4 supercell containing 96 atoms (in case of no vacancies). PBE is used as XC functional while a rotationally invariant Hubbard U correction was applied to the d orbital of V with a U value of 3.25 eV. See more details in the paper.

en: On-the-fly assessment of diffusion barriers of disordered transition metal oxyfluorides using local descriptors

big-map

display_name: big-map

fet-open

display_name: fet-open

lirichfcc

display_name: lirichfcc

lithium-diffusion

display_name: lithium-diffusion

machine-learning

display_name: machine-learning

nudged-elastic-band

display_name: nudged-elastic-band


en: This record contains the experimental results of the first ultrafast spectroscopic investigation of the electronic properties of SmB6, proposed to realize a Kondo topological insulator.  We employ a multi-temperature model to extract the electron-phonon coupling constant in the range 0.13-0.04, within the assumption of a strong coupling to the optical phonon modes in the range 10-19 meV.

en: SmB6 electron-phonon coupling constant from time- and angle-resolved photoelectron spectroscopy

electron-phonon-coupling

display_name: electron-phonon-coupling

electronic-bands

display_name: electronic-bands

experimental

display_name: experimental

kondo-system

display_name: kondo-system


en: In Peierls-distorted materials, photoexcitation leads to a strongly coupled transient response between structural and electronic degrees of freedom, always measured independently of each other. Here we use transient reflectivity in the extreme ultraviolet to quantify both responses in photoexcited bismuth in a single measurement. With the help of first-principles calculations based on density-functional theory (DFT) and time-dependent DFT, the real-space atomic motion and the temperature of both electrons and holes as a function of time are captured simultaneously, retrieving an anticorrelation between the A1g phonon dynamics and carrier temperature. The results reveal a coherent, bi-directional energy exchange between carriers and phonons, which is a dynamical counterpart of the static Peierls-Jones distortion, providing first-time validation of previous theoretical predictions.

en: Coherent energy exchange between carriers and phonons in Peierls-distorted bismuth unveiled by broadband XUV pulses

absorption-spectrum

display_name: absorption-spectrum

bismuth

display_name: bismuth

cscs

display_name: cscs

density-functional-theory

display_name: density-functional-theory

density-of-states

display_name: density-of-states

extreme-ultraviolet

display_name: extreme-ultraviolet

investissements-davenir

display_name: investissements-davenir

marvelosp

display_name: marvelosp

photoexcitation

display_name: photoexcitation

real-space-atomic-motion

display_name: real-space-atomic-motion

snsf

display_name: snsf

transient-reflectivity

display_name: transient-reflectivity


en: Skutterudites are crystals with a cagelike structure that can be augmented with filler atoms ("rattlers"), usually leading to a reduction in thermal conductivity that can be exploited for thermoelectric applications. Here, we leverage the recently introduced Wigner formulation of thermal transport to elucidate the microscopic physics underlying heat conduction in skutterudites, showing that filler atoms can drive a crossover from the Boltzmann to the Wigner regimes of thermal transport, i.e., from particlelike conduction to wavelike tunneling. At temperatures where the thermoelectric efficiency of skutterudites is largest, wavelike tunneling can become comparable to particlelike propagation. We define a Boltzmann deviation descriptor able to differentiate the two regimes and relate the competition between the two mechanisms to the materials' chemistry, providing a design strategy to select rattlers and identify optimal compositions for thermoelectric applications.

en: Crossover from Boltzmann to Wigner thermal transport in thermoelectric skutterudites

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).

marvel

display_name: marvel

phonons

display_name: phonons

thermal-conductivity

display_name: thermal-conductivity

thermoelectrics

display_name: thermoelectrics


en:
The transport and optical properties of semiconducting transition metal dichalcogenides around room temperature are dictated by electron-phonon scattering mechanisms within a complex, spin-textured and multi-valley electronic landscape. The relative positions of the valleys are critical, yet they are sensitive to external parameters and very difficult to determine directly. We propose a first-principles model as a function of valley positions to calculate carrier mobility and Kerr rotation angles, and apply it to MoS₂, WS₂, MoSe₂, and WSe₂. The model brings valuable insights, as well as quantitative predictions of macroscopic properties for a wide range of carrier density. The doping-dependant mobility displays a characteristic peak, the height depending on the position of the valleys. In parallel, the Kerr rotation signal is enhanced when same spin-valleys are aligned, and quenched when opposite spin-valleys are populated. We provide guidelines to optimize and correlate these quantities with respect to experimental parameters, as well as the theoretical support for in situ characterization of the valley positions.
The dataset contains the necessary data, a jupyter notebook, a supporting python library, and a small app with a simple user interface to reproduce the results.

en: The impact of valley profile on the mobility and Kerr rotation of transition metal dichalcogenides

materialscloud

en: Materials Cloud

electron-phonon-coupling

display_name: electron-phonon-coupling

kerr-angle

display_name: kerr-angle

transport

display_name: transport


en: In this record we provide data to support our recent findings related to carbon nanotube based quantum dots for tunable terahertz detection. Generating and detecting radiation in the technologically relevant range of the so-called terahertz gap (0.1–10 THz) is challenging because of a lack of efficient sources and detectors. Quantum dots in carbon nanotubes have shown great potential to build sensitive terahertz detectors, usually based on photon-assisted tunneling. A recently reported mechanism combining resonant quantum dot transitions and tunneling barrier asymmetries results in a narrow linewidth photocurrent response with a large signal-to-noise ratio under weak THz radiation. That device was sensitive to one frequency, corresponding to transitions between equidistant quantized states. In this work we show, using numerical simulations together with scanning tunneling spectroscopy studies of a defect-induced metallic zigzag single-walled carbon nanotube quantum dot, that breaking simultaneously various symmetries in metallic nanotube quantum dots of arbitrary chirality strongly relaxes the selection rules in the electric dipole approximation and removes energy degeneracies. This leads to a richer set of allowed optical transitions spanning frequencies from 1 THz to several tens of THz, for a ∼10 nm quantum dot. Based on these findings, we propose a terahertz detector device based on a metallic single-walled carbon nanotube quantum dot defined by artificial defects. Depending on its length and contacts transparency, the operating regimes range from a high-resolution gate-tunable terahertz sensor to a broadband terahertz detector. Our calculations indicate that the device is largely unaffected by temperatures up to 100 K, making carbon nanotube quantum dots with broken symmetries a promising platform to design tunable terahertz detectors that could operate at liquid nitrogen temperatures.

en: Metallic carbon nanotube quantum dots with broken symmetries as a platform for tunable terahertz detection

ab-initio

display_name: ab-initio

carbon-nanotubes

display_name: carbon-nanotubes

cscs

display_name: cscs

terahertz-detector

display_name: terahertz-detector