cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.24435/materialscloud:3s-gk
title: Koopmans spectral functionals: an open-source periodic-boundary implementation

description: Koopmans' spectral  functionals aim to describe simultaneously ground state properties and charged excitations of atoms, molecules, nanostructures and periodic crystals. This is achieved augmenting standard density functionals with simple but physically motivated orbital-density-dependent corrections. These corrections act on a set of localized orbitals that, in periodic systems, resembles maximally localized Wannier function. At variance with a direct supercell implementation, we discuss here i) the complex but efficient formalism required for a periodic-boundary code using explicit Brillouin zone sampling, and ii) the calculation of the screened Koopmans' corrections with density-functional perturbation theory. In addition to delivering improved scaling with system size, the present development makes the calculation of band structures with Koopmans functionals straightforward. The implementation in the Quantum ESPRESSO distribution and the application to prototypical insulating and semiconducting systems are presented and discussed.
DOI: 10.24435/materialscloud:x0-9w
title: Magnetic exchange interactions in monolayer CrI₃ from many-body wavefunction calculations

description: The marked interplay between the crystalline, electronic, and magnetic structure of atomically thin magnets has been regarded as the key feature for designing next-generation magneto-optoelectronic devices. In this respect, a detailed understanding of the microscopic interactions underlying the magnetic response of these crystals is of primary importance. Here, we combine model Hamiltonians with multireference configuration interaction wavefunctions to accurately determine the strength of the spin couplings in the prototypical single-layer magnet CrI₃. Our calculations identify the (ferromagnetic) Heisenberg exchange interaction J = −1.44 meV as the dominant term, being the inter-site magnetic anisotropies substantially weaker. We also find that single-layer CrI₃ features an out-of-plane easy axis ensuing from a single-ion anisotropy A = −0.10 meV, and predict g-tensor in-plane components gxx = gyy = 1.90 and out-of-plane component gzz  = 1.92. In addition, we assess the performance of a dozen widely used density functionals against our accurate correlated wavefunctions calculations and available experimental data, thereby establishing reference results for future first-principles investigations. Overall, our findings offer a firm theoretical ground to recent experimental observations.
DOI: 10.24435/materialscloud:ex-va
title: High-performance NiOOH/FeOOH electrode for OER catalysis

description: The outstanding performance of NiOOH/FeOOH-based oxygen evolution reaction (OER) catalysts is rationalized in terms of a bifunctional mechanism involving two distinct active sites. In this mechanism, the OOH_ads reaction intermediate, which unfavorably affects the overall OER activity due to the linear scaling relationship, is replaced by O2 adsorbed at the active site on FeOOH, and H_ads adsorbed at the NiOOH substrate. Here, we use the computational hydrogen electrode method to assess promising models of both the FeOOH catalyst and the NiOOH hydrogen acceptor. These two materials are interfaced in various ways to evaluate their performance as bifunctional OER catalysts. In some cases, overpotentials as low as 0.16 V are found, supporting the bifunctional mechanism as a means to overcome the limitations imposed by linear scaling relationships.
DOI: 10.24435/materialscloud:1m-6f
title: Persistence of a surface state arc in the topologically trivial phase of MoTe2

description: This record contains the experimental band structure of MoTe2. The material exhibits a structural phase transition at approximately 240 K, and in the low-temperature 1T' phase is expected to realize the type-II Weyl semimetal phase. In our data we compare the band structure and the Fermi surface in the topological and in the trivial (1T'') phase. We report the existence of large surface arc, which is persistent across the topological phase transition, and we conclude that its observation cannot be taken alone as a smoking gun of the Weyl semimetal phase. The study is completed by a spin-resolved ARPES study of the bulk electronic properties in the low-temperature topological phase
DOI: 10.24435/materialscloud:ke-y1
title: High-performance NiOOH/FeOOH electrode for OER catalysis

description: The outstanding performance of NiOOH/FeOOH-based oxygen evolution reaction (OER) catalysts is rationalized in terms of a bifunctional mechanism involving two distinct active sites. In this mechanism, the OOH_ads reaction intermediate, which unfavorably affects the overall OER activity due to the linear scaling relationship, is replaced by O2 adsorbed at the active site on FeOOH, and H_ads adsorbed at the NiOOH substrate. Here, we use the computational hydrogen electrode method to assess promising models of both the FeOOH catalyst and the NiOOH hydrogen acceptor. These two materials are interfaced in various ways to evaluate their performance as bifunctional OER catalysts. In some cases, overpotentials as low as 0.16 V are found, supporting the bifunctional mechanism as a means to overcome the limitations imposed by linear scaling relationships.
DOI: 10.24435/materialscloud:ef-9x
title: Persistence of a surface state arc in the topologically trivial phase of MoTe2

description: This record contains the experimental band structure of MoTe2. The material exhibits a structural phase transition at approximately 240 K, and in the low-temperature 1T' phase is expected to realize the type-II Weyl semimetal phase. In our data we compare the band structure and the Fermi surface in the topological and in the trivial (1T'') phase. We report the existence of large surface arc, which is persistent across the topological phase transition, and we conclude that its observation cannot be taken alone as a smoking gun of the Weyl semimetal phase. The study is completed by a spin-resolved ARPES study of the bulk electronic properties in the low-temperature topological phase
DOI: 10.24435/materialscloud:pr-mg
title: Modeling the Ga/As binary system across temperatures and compositions from first principles

description: Materials composed of elements from the third and fifth columns of the periodic table display a very rich behavior, with the phase diagram usually containing a metallic liquid phase and a polar semiconducting solid. As a consequence, it is very hard to achieve transferable empirical models of interactions between the atoms that can reliably predict their behavior across the temperature and composition range that is relevant to the study of the synthesis and properties of III/V nanostructures and devices. We present a machine-learning potential trained on density functional theory reference data that provides a general-purpose model for the Ga/As system. We provide a series of stringent tests that showcase the accuracy of the potential, and its applicability across the whole binary phase space, computing with ab initio accuracy a large number of finite-temperature properties as well as the location of phase boundaries. We also show how a committee model can be used to reliably determine the uncertainty induced by the limitations of the machine-learning model on its predictions, to identify regions of phase space that are predicted with insufficient accuracy, and to iteratively refine the training set to achieve consistent, reliable modeling.
DOI: 10.24435/materialscloud:q5-tn
title: Plasmon energy changes in FeMo14C15B6Erx (x=0-2) bulk metallic glass during in-situ heating

description: Variations of volume plasmon energy of both ribbon and bulk FeMo14C15B6Erx (x=0-2) metallic glasses were measured as a function of the temperature in an analytical transmission electron microscope using valence electron energy loss spectroscopy (VEELS). The plasmon energy was found to decrease with increasing temperature, due not only to thermal expansion but also to chemical reordering in the glasses. The chemical reordering stimulates a specific solute cluster formation; M23(C, B)6 solute clusters began to form above about 200°C in both ribbon and bulk FeMo14C15B6Erx (x=0, 0.5, 1) metallic glasses. The formation of the M23(C, B)6 solute clusters was only found above 400°C in the ribbon FeMo14C15B6Er2 metallic glass, indicating inhibition of the M23(C, B)6 solute clusters occurred owing to the formation of Er-(C, B) complexes/clusters. The Er-(C, B) complexes/clusters were formed in the cooling process of the sample fabrication. In contrast to the ribbon sample, the formation of the M23(C, B)6 solute clusters did not occur in the bulk FeMo14C15B6Er2 metallic glass during heating. The amount of the Er-(C, B) complexes/clusters in the bulk sample was larger than that in the ribbon sample because of the slow cooling rate in the bulk sample fabrication. Because the solute carbon and boron atoms were mostly consumed by the formation of Er-(C, B) complexes/clusters in the bulk FeMo14C15B6Er2 metallic glass, the formation of M23(C, B)6 solute clusters was suppressed. This study demonstrates that chemical reordering during the relaxation of metallic glasses can be detected by the VEELS, providing valuable insight into the relaxation stage of metallic glass during heating.
DOI: 10.24435/materialscloud:1a-v0
title: Plasmon energy changes in FeMo14C15B6Erx (x=0-2) bulk metallic glass during in-situ heating

description: Variations of volume plasmon energy of both ribbon and bulk FeMo14C15B6Erx (x=0-2) metallic glasses were measured as a function of the temperature in an analytical transmission electron microscope using valence electron energy loss spectroscopy (VEELS). The plasmon energy was found to decrease with increasing temperature, due not only to thermal expansion but also to chemical reordering in the glasses. The chemical reordering stimulates a specific solute cluster formation; M23(C, B)6 solute clusters began to form above about 200°C in both ribbon and bulk FeMo14C15B6Erx (x=0, 0.5, 1) metallic glasses. The formation of the M23(C, B)6 solute clusters was only found above 400°C in the ribbon FeMo14C15B6Er2 metallic glass, indicating inhibition of the M23(C, B)6 solute clusters occurred owing to the formation of Er-(C, B) complexes/clusters. The Er-(C, B) complexes/clusters were formed in the cooling process of the sample fabrication. In contrast to the ribbon sample, the formation of the M23(C, B)6 solute clusters did not occur in the bulk FeMo14C15B6Er2 metallic glass during heating. The amount of the Er-(C, B) complexes/clusters in the bulk sample was larger than that in the ribbon sample because of the slow cooling rate in the bulk sample fabrication. Because the solute carbon and boron atoms were mostly consumed by the formation of Er-(C, B) complexes/clusters in the bulk FeMo14C15B6Er2 metallic glass, the formation of M23(C, B)6 solute clusters was suppressed. This study demonstrates that chemical reordering during the relaxation of metallic glasses can be detected by the VEELS, providing valuable insight into the relaxation stage of metallic glass during heating.
DOI: 10.24435/materialscloud:sn-np
title: Understanding thermal quenching of photoluminescence in oxynitride phosphors from first principles

description: Understanding the physical mechanisms behind thermal effects in phosphors is crucial for white light-emitting device (WLEDs) applications, as thermal quenching of their photoluminescence might render them useless. We analyze from first-principles, before and after absorption/emission of light, two chemically close Eu-doped Ba₃Si₆O₁₂N₂ and Ba₃Si₆O₉N₄ crystals for WLEDs. The first one has an almost constant emission intensity with increasing temperature whereas the other one does not. Our results, in which the Eu-5d levels are obtained inside the band gap thanks to the removal of an electron from the 4f⁷ shell, and the atomic neighborhood properly relaxed in the excited state, attributes the above-mentioned experimental difference to an autoionization model of the thermal quenching, based on the energy difference between Eu 5d and the conduction band minimum. Our depleted-shifted 4f method can identify luminescent centers and therefore allows for effective crystal site engineering of luminescent centers in phosphors from first principles.
DOI: 10.24435/materialscloud:z9-jf
title: Understanding thermal quenching of photoluminescence in oxynitride phosphors from first principles

description: Understanding the physical mechanisms behind thermal effects in phosphors is crucial for white light-emitting device (WLEDs) applications, as thermal quenching of their photoluminescence might render them useless. We analyze from first-principles, before and after absorption/emission of light, two chemically close Eu-doped Ba₃Si₆O₁₂N₂ and Ba₃Si₆O₉N₄ crystals for WLEDs. The first one has an almost constant emission intensity with increasing temperature whereas the other one does not. Our results, in which the Eu-5d levels are obtained inside the band gap thanks to the removal of an electron from the 4f⁷ shell, and the atomic neighborhood properly relaxed in the excited state, attributes the above-mentioned experimental difference to an autoionization model of the thermal quenching, based on the energy difference between Eu 5d and the conduction band minimum. Our depleted-shifted 4f method can identify luminescent centers and therefore allows for effective crystal site engineering of luminescent centers in phosphors from first principles.
DOI: 10.24435/materialscloud:tb-dq
title: Modeling the Ga/As binary system across temperatures and compositions from first principles

description: Materials composed of elements from the third and fifth columns of the periodic table display a very rich behavior, with the phase diagram usually containing a metallic liquid phase and a polar semiconducting solid. As a consequence, it is very hard to achieve transferable empirical models of interactions between the atoms that can reliably predict their behavior across the temperature and composition range that is relevant to the study of the synthesis and properties of III/V nanostructures and devices. We present a machine-learning potential trained on density functional theory reference data that provides a general-purpose model for the Ga/As system. We provide a series of stringent tests that showcase the accuracy of the potential, and its applicability across the whole binary phase space, computing with ab initio accuracy a large number of finite-temperature properties as well as the location of phase boundaries. We also show how a committee model can be used to reliably determine the uncertainty induced by the limitations of the machine-learning model on its predictions, to identify regions of phase space that are predicted with insufficient accuracy, and to iteratively refine the training set to achieve consistent, reliable modeling.
DOI: 10.24435/materialscloud:c9-1d
title: Modeling the Ga/As binary system across temperatures and compositions from first principles

description: Materials composed of elements from the third and fifth columns of the periodic table display a very rich behavior, with the phase diagram usually containing a metallic liquid phase and a polar semiconducting solid. As a consequence, it is very hard to achieve transferable empirical models of interactions between the atoms that can reliably predict their behavior across the temperature and composition range that is relevant to the study of the synthesis and properties of III/V nanostructures and devices. We present a machine-learning potential trained on density functional theory reference data that provides a general-purpose model for the Ga/As system. We provide a series of stringent tests that showcase the accuracy of the potential, and its applicability across the whole binary phase space, computing with ab initio accuracy a large number of finite-temperature properties as well as the location of phase boundaries. We also show how a committee model can be used to reliably determine the uncertainty induced by the limitations of the machine-learning model on its predictions, to identify regions of phase space that are predicted with insufficient accuracy, and to iteratively refine the training set to achieve consistent, reliable modeling.
DOI: 10.24435/materialscloud:s4-g3
title: Yield strength and misfit volumes of NiCoCr and implications for short-range-order

description: The face-centered cubic medium-entropy alloy NiCoCr has received considerable attention for its good mechanical properties, uncertain stacking fault energy, etc, some of which have been attributed to chemical short-range order (SRO). Here, we examine the yield strength and misfit volumes of NiCoCr to determine whether SRO has measurably influenced mechanical properties. Polycrystalline strengths show no systematic trend with different processing conditions. Measured misfit volumes in NiCoCr are consistent with those in random binaries. Yield strength prediction of a random NiCoCr alloy matches well with experiments. Finally, we show that standard spin-polarized density functional theory (DFT) calculations of misfit volumes are not accurate for NiCoCr. This implies that DFT may be inaccurate for other subtle structural quantities such as atom-atom bond distance so that caution is required in drawing conclusions about NiCoCr based on DFT. These findings all lead to the conclusion that, under typical processing conditions, SRO in NiCoCr is either negligible or has no systematic measurable effect on strength.
DOI: 10.24435/materialscloud:n3-3g
title: Yield strength and misfit volumes of NiCoCr and implications for short-range-order

description: The face-centered cubic medium-entropy alloy NiCoCr has received considerable attention for its good mechanical properties, uncertain stacking fault energy, etc, some of which have been attributed to chemical short-range order (SRO). Here, we examine the yield strength and misfit volumes of NiCoCr to determine whether SRO has measurably influenced mechanical properties. Polycrystalline strengths show no systematic trend with different processing conditions. Measured misfit volumes in NiCoCr are consistent with those in random binaries. Yield strength prediction of a random NiCoCr alloy matches well with experiments. Finally, we show that standard spin-polarized density functional theory (DFT) calculations of misfit volumes are not accurate for NiCoCr. This implies that DFT may be inaccurate for other subtle structural quantities such as atom-atom bond distance so that caution is required in drawing conclusions about NiCoCr based on DFT. These findings all lead to the conclusion that, under typical processing conditions, SRO in NiCoCr is either negligible or has no systematic measurable effect on strength.
DOI: 10.24435/materialscloud:t0-hn
title: High-throughput calculation of interlayer van der Waals force validated with experimental measurements

description: Interlayer binding strength is an important property of two-dimensional (2D) materials in various occasions including exfoliation and heterostructure construction. Though there are already many calculations and experimental measurements for interlayer binding energy, few calculation references regarding the interlayer binding force can be found which is often the quantity been directly measured in experiments. Moreover, binding force rather than binding energy should be considered more closely related to whether a layered structure can be exfoliated or not under certain circumstances. To our best knowledge, there exists no such a database for 2D materials interlayer binding forces. In this work, with a descent algorithm designed to work with first-principles code, maximum interlayer binding force with the accuracy down to 1 meV/Å per atom is directly calculated for 230 common 2D materials using both the vdW-DF2 and optB88-vdW functionals. The results show significant inconsistency between the trend of maximum binding energies and binding forces, which means large binding energy does not necessarily lead to large binding force. Based on these results, a relationship between the two quantities is found valid for more than 200 different systems among the total of 230. To confirm the validity of these calculated forces, interlayer force measurements are performed for graphene (G), h-BN and In2Se3 by coating them on tipless probes and measuring the cohesive force using atomic force microscopy. The measurements show F_G > F_h-BN > F_In2Se3 , which is consistent with the calculated results, and the estimated per-unit-area force is of the same magnitude to the predicted values. Our work can help determine appropriate exfoliation methods for different 2D materials, and provide a reliable reference for interlayer adhesion studies.
DOI: 10.24435/materialscloud:7z-pe
title: High-throughput calculation of interlayer van der Waals force validated with experimental measurements

description: Interlayer binding strength is an important property of two-dimensional (2D) materials in various occasions including exfoliation and heterostructure construction. Though there are already many calculations and experimental measurements for interlayer binding energy, few calculation references regarding the interlayer binding force can be found which is often the quantity been directly measured in experiments. Moreover, binding force rather than binding energy should be considered more closely related to whether a layered structure can be exfoliated or not under certain circumstances. To our best knowledge, there exists no such a database for 2D materials interlayer binding forces. In this work, with a descent algorithm designed to work with first-principles code, maximum interlayer binding force with the accuracy down to 1 meV/Å per atom is directly calculated for 230 common 2D materials using both the vdW-DF2 and optB88-vdW functionals. The results show significant inconsistency between the trend of maximum binding energies and binding forces, which means large binding energy does not necessarily lead to large binding force. Based on these results, a relationship between the two quantities is found valid for more than 200 different systems among the total of 230. To confirm the validity of these calculated forces, interlayer force measurements are performed for graphene (G), h-BN and In2Se3 by coating them on tipless probes and measuring the cohesive force using atomic force microscopy. The measurements show F_G > F_h-BN > F_In2Se3 , which is consistent with the calculated results, and the estimated per-unit-area force is of the same magnitude to the predicted values. Our work can help determine appropriate exfoliation methods for different 2D materials, and provide a reliable reference for interlayer adhesion studies.