cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.24435/materialscloud:4p-kd
title: Impact of quantum-chemical metrics on the machine learning prediction of electron density

description: Machine learning (ML) algorithms have undergone an explosive development impacting every aspect of computational chemistry. To obtain reliable predictions, one needs to maintain the proper balance between the black-box nature of ML frameworks and the physics of the target properties. One of the most appealing quantum-chemical properties for regression models is the electron density, and some of us recently proposed a transferable and scalable model based on the decomposition of the density onto an atom-centered basis set. The decomposition, as well as the training of the model, is at its core a minimization of some loss function, which can be arbitrarily chosen and may lead to results of different quality. Well-studied in the context of density fitting (DF), the impact of the metric on the performance of ML models has not been analyzed yet. In this work, we compare predictions obtained using the overlap and the Coulomb repulsion metrics for both the decomposition and training. As expected, the Coulomb metric used as both the DF and ML loss functions leads to the best results for the electrostatic potential and dipole moments. The origin of this difference lies in the fact that the model is not constrained to predict densities that integrate to the exact number of electrons N. Since an a posteriori correction for the number of electrons decreases the errors, we proposed a modification of the model where N is included directly into the kernel function, which allowed to lower the errors on the test and out-of-sample sets.
DOI: 10.24435/materialscloud:be-eq
title: Correlated states in twisted double bilayer graphene

description: Electron–electron interactions play an important role in graphene and related systems and can induce exotic quantum states, especially in a stacked bilayer with a small twist angle. For bilayer graphene where the two layers are twisted by the 'magic angle', flat band and strong many-body effects lead to correlated insulating states and superconductivity. In contrast to monolayer graphene, the band structure of untwisted bilayer graphene can be further tuned by a displacement field, providing an extra degree of freedom to control the flat band that should appear when two bilayers are stacked on top of each other. Here, we report the discovery and characterization of displacement field-tunable electronic phases in twisted double bilayer graphene. We observe insulating states at a half-filled conduction band in an intermediate range of displacement fields. Furthermore, the resistance gap in the correlated insulator increases with respect to the in-plane magnetic fields and we find that the g factor, according to the spin Zeeman effect, is ~2, indicating spin polarization at half-filling. These results establish twisted double bilayer graphene as an easily tunable platform for exploring quantum many-body states.
DOI: 10.24435/materialscloud:s9-pt
title: Correlated states in twisted double bilayer graphene

description: Electron–electron interactions play an important role in graphene and related systems and can induce exotic quantum states, especially in a stacked bilayer with a small twist angle. For bilayer graphene where the two layers are twisted by the 'magic angle', flat band and strong many-body effects lead to correlated insulating states and superconductivity. In contrast to monolayer graphene, the band structure of untwisted bilayer graphene can be further tuned by a displacement field, providing an extra degree of freedom to control the flat band that should appear when two bilayers are stacked on top of each other. Here, we report the discovery and characterization of displacement field-tunable electronic phases in twisted double bilayer graphene. We observe insulating states at a half-filled conduction band in an intermediate range of displacement fields. Furthermore, the resistance gap in the correlated insulator increases with respect to the in-plane magnetic fields and we find that the g factor, according to the spin Zeeman effect, is ~2, indicating spin polarization at half-filling. These results establish twisted double bilayer graphene as an easily tunable platform for exploring quantum many-body states.
DOI: 10.24435/materialscloud:p9-q7
title: Towards constant potential modeling of CO-CO coupling at liquid water-Cu(100) interfaces

description: We have studied electrochemical *CO-*CO coupling in explicit electrolyte with density functional theory, molecular dynamics, and metadynamics. We considered both the *CO-*CO coupling reaction and the charging process required to keep the potential constant. The charging process consists of transferring explicit cations from the electrolyte and electrons from the potentiostat to the interface. Under constant charge conditions (non-constant electrostatic potential), the *CO-*CO coupling reaction energies are relative insensitive to the charge state at the interface and the electrolyte composition and the reaction occurs with co-adsorption of water. Under constant potential conditions, the *CO-*CO coupling reaction is stabilized at lower potentials because of charging and the reaction is influenced by the electrolyte composition.
Here we have collected the data from the eight AIMD metadynamics simulations conducted in the study. Each AIMD data tar.gz file contains the VASP input files (INCAR, KPOINTS, POTCAR, ICONST), the VASP output files for the full AIMD run (OUTCAR*, PENALTYPOT), python scripts that have been used to analyze the AIMD run, data files made by those scripts (*dat), a folder (0/) used to set up single point calculations of workfunction and Bader chages at 0.125 ps intervals along the AIMD trajectory, and one folder (*.000ps) containing an example of a workfunction and Bader charge calculation.
DOI: 10.24435/materialscloud:qd-f7
title: Towards constant potential modeling of CO-CO coupling at liquid water-Cu(100) interfaces

description: We have studied electrochemical *CO-*CO coupling in explicit electrolyte with density functional theory, molecular dynamics, and metadynamics. We considered both the *CO-*CO coupling reaction and the charging process required to keep the potential constant. The charging process consists of transferring explicit cations from the electrolyte and electrons from the potentiostat to the interface. Under constant charge conditions (non-constant electrostatic potential), the *CO-*CO coupling reaction energies are relative insensitive to the charge state at the interface and the electrolyte composition and the reaction occurs with co-adsorption of water. Under constant potential conditions, the *CO-*CO coupling reaction is stabilized at lower potentials because of charging and the reaction is influenced by the electrolyte composition.
Here we have collected the data from the eight AIMD metadynamics simulations conducted in the study. Each AIMD data tar.gz file contains the VASP input files (INCAR, KPOINTS, POTCAR, ICONST), the VASP output files for the full AIMD run (OUTCAR*, PENALTYPOT), python scripts that have been used to analyze the AIMD run, data files made by those scripts (*dat), a folder (0/) used to set up single point calculations of workfunction and Bader chages at 0.125 ps intervals along the AIMD trajectory, and one folder (*.000ps) containing an example of a workfunction and Bader charge calculation.
DOI: 10.24435/materialscloud:ws-za
title: Enhanced ultrafast relaxation rate in the Weyl semimetal phase of MoTe2 measured by time- and angle-resolved photoelectron spectroscopy

description: This record contains the results of the first experimental investigation of the change in the electron dynamics across the topological phase transition from the type-II Weyl semimetal phase of MoTe2 to the trivial phase. By using the capability of time-resolved ARPES to access the unoccupied density of states, we succeed in transiently populating the Weyl points, which are otherwise above the Fermi level and out of the reach of conventional ARPES. We observe a bottleneck in the electron dynamics when the Weyl points annihilate and gaps are opened in the high-temperature trivial phase. This interpretation is supported by the observation that, in the "sister" compound WTe2 the dynamics is not affected by the change in temperature, and it is always much slower, thus reflecting the larger energy separation between the valence and conduction band.
DOI: 10.25326/6d2n-wm66
title: Atmospheric simulation chamber study: water+ice+volcanic ash + None - Cloud study - 2017-05-26
DOI: 10.25326/kdys-vb64
title: Atmospheric simulation chamber study: water+ice+mineral dust + None - Cloud study - 2019-05-06
DOI: 10.25326/ntek-nh23
title: Atmospheric simulation chamber study: water+ice+volcanic ash + None - Cloud study - 2017-05-26
DOI: 10.24435/materialscloud:x1-0w
title: Enhanced ultrafast relaxation rate in the Weyl semimetal phase of MoTe2 measured by time- and angle-resolved photoelectron spectroscopy

description: This record contains the results of the first experimental investigation of the change in the electron dynamics across the topological phase transition from the type-II Weyl semimetal phase of MoTe2 to the trivial phase. By using the capability of time-resolved ARPES to access the unoccupied density of states, we succeed in transiently populating the Weyl points, which are otherwise above the Fermi level and out of the reach of conventional ARPES. We observe a bottleneck in the electron dynamics when the Weyl points annihilate and gaps are opened in the high-temperature trivial phase. This interpretation is supported by the observation that, in the "sister" compound WTe2 the dynamics is not affected by the change in temperature, and it is always much slower, thus reflecting the larger energy separation between the valence and conduction band.
DOI: 10.25326/5fxt-8s55
title: Atmospheric simulation chamber study: water+ice+mineral dust + None - Cloud study - 2019-05-07
DOI: 10.25326/h7hc-yj91
title: Atmospheric simulation chamber study: water+ice+mineral dust + None - Cloud study - 2019-05-07
DOI: 10.24435/materialscloud:21-py
title: Prediction of yield strength in refractory body-centered-cubic High Entropy Alloys

description: Energy efficiency is motivating the search for new high-temperature metals. Some new body-centered-cubic random multicomponent "high entropy alloys (HEAs)" based on refractory elements (Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr) possess exceptional strengths at high temperatures but the physical origins of this outstanding behavior are not known.
Here, by using a recent mechanistic theory, we have computed the high-temperature (T=1300K) yield strength based on solute strengthening of over 10 million alloys within the whole Al-Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr alloy family. Also the yield strength/density has been computed.
This database enables the efficient search of new alloys with exceptional high-temperature strength.
DOI: 10.24435/materialscloud:fs-27
title: Prediction of yield strength in refractory body-centered-cubic High Entropy Alloys

description: Energy efficiency is motivating the search for new high-temperature metals. Some new body-centered-cubic random multicomponent "high entropy alloys (HEAs)" based on refractory elements (Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr) possess exceptional strengths at high temperatures but the physical origins of this outstanding behavior are not known.
Here, by using a recent mechanistic theory, we have computed the high-temperature (T=1300K) yield strength based on solute strengthening of over 10 million alloys within the whole Al-Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr alloy family. Also the yield strength/density has been computed.
This database enables the efficient search of new alloys with exceptional high-temperature strength.
DOI: 10.25326/5x59-q090
title: Atmospheric simulation chamber study: glyoxal + Sulfur dioxide + 3-pentanol + Na2SO4 seeds + OH - Cloud study - 2017-07-07
DOI: 10.25326/xe7z-ec10
title: Atmospheric simulation chamber study: glyoxal + Sulfur dioxide + 3-pentanol + Na2SO4 seeds + OH - Cloud study - 2017-07-06
DOI: 10.24435/materialscloud:gn-2p
title: Accurate optical spectra through time-dependent density functional theory based on screening-dependent hybrid functionals

description: We investigate optical absorption spectra obtained through time-dependent density functional theory (TD-DFT) based on nonempirical hybrid functionals that are designed to correctly reproduce the dielectric function. The comparison with state-of-the-art GW calculations followed by the solution of the Bethe-Salpeter equation (BSE-GW) shows close agreement for both the transition energies and the main features of the spectra. We confront TD-DFT with BSE-GW by focusing on the model dielectric function and the local exchange-correlation kernel. The present TD-DFT approach achieves the accuracy of BSE-GW at a fraction of the computational cost.
DOI: 10.25326/4hs3-m215
title: Atmospheric simulation chamber study: glyoxal + Sulfur dioxide + 3-pentanol + Na2SO4 seeds + OH - Cloud study - 2017-07-11
DOI: 10.25326/d3dd-y688
title: Atmospheric simulation chamber study: glyoxal + Sulfur dioxide + 3-pentanol + Na2SO4 seeds + OH - Cloud study - 2017-07-10
DOI: 10.25326/j1zn-x623
title: Atmospheric simulation chamber study: glyoxal + 3-pentanol + Na2SO3 seeds + OH - Cloud study - 2017-07-12
DOI: 10.24435/materialscloud:90-es
title: Accurate optical spectra through time-dependent density functional theory based on screening-dependent hybrid functionals

description: We investigate optical absorption spectra obtained through time-dependent density functional theory (TD-DFT) based on nonempirical hybrid functionals that are designed to correctly reproduce the dielectric function. The comparison with state-of-the-art GW calculations followed by the solution of the Bethe-Salpeter equation (BSE-GW) shows close agreement for both the transition energies and the main features of the spectra. We confront TD-DFT with BSE-GW by focusing on the model dielectric function and the local exchange-correlation kernel. The present TD-DFT approach achieves the accuracy of BSE-GW at a fraction of the computational cost.
DOI: 10.24435/materialscloud:f5-fe
title: Sampling enhancement by metadynamics driven by machine learning and de novo protein modelling

description: 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.
DOI: 10.25326/4841-qm92
title: Atmospheric simulation chamber study: glyoxal + 3-pentanol + Na2SO3 seeds + OH - Cloud study - 2017-07-17
DOI: 10.25326/r7t9-8x80
title: Atmospheric simulation chamber study: glyoxal + 3-pentanol + Na2SO3 seeds + OH - Cloud study - 2017-07-13
DOI: 10.25326/3m51-h075
title: Atmospheric simulation chamber study: 2-propanol + sulfur dioxide + NaCl seeds + OH - Cloud study - 2017-07-04
DOI: 10.25326/kbd6-8c07
title: Atmospheric simulation chamber study: catechol + None - Cloud study - 2021-07-27
DOI: 10.24435/materialscloud:tr-t9
title: Multi-scale approach for the prediction of atomic scale properties

description: Electronic nearsightedness is one of the fundamental principles that governs the behavior of condensed matter and supports its description in terms of local entities such as chemical bonds. 
Locality also underlies the tremendous success of machine-learning schemes that predict quantum mechanical observables -- such as the cohesive energy, the electron density, or a variety of response properties -- as a sum of atom-centred contributions, based on a short-range representation of atomic environments.
One of the main shortcomings of these approaches is their inability to capture physical effects, ranging from electrostatic interactions to quantum delocalization, which have a long-range nature. 
Here we show how to build a multi-scale scheme that combines in the same framework local and non-local information, overcoming such limitations. We show that the simplest version of such features can be put in formal correspondence with a multipole expansion of permanent electrostatics. The data-driven nature of the model construction, however, makes this simple form suitable to tackle also different types of delocalized and collective effects. We present several examples that range from molecular physics to surface science and biophysics, demonstrating the ability of this multi-scale approach to model interactions driven by electrostatics, polarization and dispersion, as well as the cooperative behavior of dielectric response functions.
DOI: 10.25326/d7y1-s078
title: Atmospheric simulation chamber study: hydroxyacetone + hydrogen peroxide + OH - Cloud study - 2017-07-20
DOI: 10.25326/yrjg-es08
title: Atmospheric simulation chamber study: hydroxyacetone + hydrogen peroxide + OH - Cloud study - 2017-07-18
DOI: 10.24435/materialscloud:f7-f5
title: Multi-scale approach for the prediction of atomic scale properties

description: Electronic nearsightedness is one of the fundamental principles that governs the behavior of condensed matter and supports its description in terms of local entities such as chemical bonds. 
Locality also underlies the tremendous success of machine-learning schemes that predict quantum mechanical observables -- such as the cohesive energy, the electron density, or a variety of response properties -- as a sum of atom-centred contributions, based on a short-range representation of atomic environments.
One of the main shortcomings of these approaches is their inability to capture physical effects, ranging from electrostatic interactions to quantum delocalization, which have a long-range nature. 
Here we show how to build a multi-scale scheme that combines in the same framework local and non-local information, overcoming such limitations. We show that the simplest version of such features can be put in formal correspondence with a multipole expansion of permanent electrostatics. The data-driven nature of the model construction, however, makes this simple form suitable to tackle also different types of delocalized and collective effects. We present several examples that range from molecular physics to surface science and biophysics, demonstrating the ability of this multi-scale approach to model interactions driven by electrostatics, polarization and dispersion, as well as the cooperative behavior of dielectric response functions.
DOI: 10.24435/materialscloud:rz-fj
title: Transport signatures of temperature-induced chemical potential shift and Lifshitz transition in layered type-II Weyl semimetal TaIrTe4

description: 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.
DOI: 10.25326/4vyf-qg62
title: Atmospheric simulation chamber study: hydroxyacetone + hydrogen peroxide + OH - Cloud study - 2017-07-21
DOI: 10.25326/78zm-8t09
title: Atmospheric simulation chamber study: hydroxyacetone + hydrogen peroxide + methylamine + OH - Cloud study - 2017-07-24
DOI: 10.24435/materialscloud:bg-z9
title: Transport signatures of temperature-induced chemical potential shift and Lifshitz transition in layered type-II Weyl semimetal TaIrTe4

description: 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.
DOI: 10.24435/materialscloud:jt-32
title: Ab initio electron-phonon interactions in correlated electron systems

description: Electron-phonon (e-ph) interactions are pervasive in condensed matter, governing phenomena such as transport, superconductivity, charge-density waves, polarons, and metal-insulator transitions. First-principles approaches enable accurate calculations of e-ph interactions in a wide range of solids. However, they remain an open challenge in correlated electron systems (CES), where density functional theory often fails to describe the ground state. Therefore reliable e-ph calculations remain out of reach for many transition metal oxides, high-temperature superconductors, Mott insulators, planetary materials, and multiferroics. Here we show first-principles calculations of e-ph interactions in CES, using the framework of Hubbard-corrected density functional theory (DFT+U) and its linear response extension (DFPT+U), which can describe the electronic structure and lattice dynamics of many CES. We showcase the accuracy of this approach for a prototypical Mott system, CoO, carrying out a detailed investigation of its e-ph interactions and electron spectral functions. While standard DFPT gives unphysically divergent and short-ranged e-ph interactions, DFPT+U is shown to remove the divergences and properly account for the long-range Fröhlich interaction, allowing us to model polaron effects in a Mott insulator. Our work establishes a broadly applicable and affordable approach for quantitative studies of e-ph interactions in CES, a novel theoretical tool to interpret experiments in this broad class of materials.