AndreaBozzo/ceres-open-data-index huggingface dataset:
Berry curvature signatures in chiroptical excitonic transitions

The topology of the electronic band structure of solids can be described by its Berry curvature distribution across the Brillouin zone. We theoretically introduce and experimentally demonstrate a general methodology based on the measurement of energy- and momentum-resolved optical transition rates, allowing to reveal signatures of Berry curvature texture in reciprocal space. By performing time- and angle-resolved photoemission spectroscopy of atomically thin WSe₂ using polarization-modulated excitations, we demonstrate that excitons become an asset in extracting the quantum geometrical properties of solids. We also investigate the resilience of our measurement protocol against ultrafast scattering processes following direct chiroptical transitions.
Here we provide the data presented in the paper referenced below. The data set contains the results of the first-principle calculations of the exciton properties, python scripts for solving the real-time dynamics, and python scripts for generating the plots. We also provide the raw measured photoemission intensity along with the post-processing and corresponding plotting scripts.
A more detailed description is provided in the README.md files.

Tags: experimental, first-principles, topological-materials, two-dimensional
Model structures of the Si(100)-SiO₂ interface

The record contains model structures of the Si(100)-SiO₂ interface with disordered and crystalline oxides. The models have been purposely designed in order to match a large variety of atomic-scale experimental data. In particular, the models with a disordered oxide reproduce the amorphous nature of the oxide and the density of the oxide near the substrate. The atomic structure does not show any coordination defects consistent with the low measured density of interfacial defect states. The transition region includes intermediate oxidation states of Si in accord with photoemission experiments. Also the dielectric properties agree with the experimental characterization. Hence, the present models synthesize the present status of our experimental knowledge on the Si(100)–SiO₂ interface and provide a solid and necessary basis for future investigations in the area of gate stacks for Si-based microelectronics.

Tags: atomic-coordinates, crystalline-amorphous-transition-structure, density-functional-theory, epfl, snsf
Probing the effects of broken symmetries in machine learning

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

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

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

Tags: equivariance, machine-learning, marvelp2, water
Exploring chemical space in the search for improved Azoheteroarene-based photoswitches

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

Tags: azobenzene-derivatives, computations, photoswitches, td-dft
Viscosity in water from first-principles and deep-neural-network simulations

We report on an extensive study of the viscosity of liquid water at near-ambient conditions, performed within the Green-Kubo theory of linear response and equilibrium ab initio molecular dynamics (AIMD), based on density-functional theory (DFT). In order to cope with the long simulation times necessary to achieve an acceptable statistical accuracy, our ab initio approach is enhanced with deep-neural-network potentials (NNP). This approach is first validated against AIMD results, obtained by using the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and paying careful attention to crucial, yet often overlooked, aspects of the statistical data analysis. Then, we train a second NNP to a dataset generated from the strongly-constrained and appropriately-normed SCAN-DFT functional. Once the error resulting from the imperfect prediction of the melting line is offset by referring the simulated temperature to the theoretical melting one, our SCAN DFT predictions of the shear viscosity of water are in very good agreement with experiments.

Tags: ab-initio, machine-learning, molecular-dynamics-simulation, neural-networks, transport, viscosity, water
A fourth-generation high-dimensional neural network potential with accurate electrostatics including non-local charge transfer

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

Tags: dft, machine-learning-potentials, non-local-charge-transfer, snsf
Comparative density functional theory study for predicting oxygen reduction activity of single-atom catalyst

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

Tags: density-functional-theory, exchange-correlation-functional, oxygen-reduction-reaction, single-atom-catalyst
Profiling novel high-conductivity 2D semiconductors

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

Tags: 2d-materials, electron-phonon-coupling, marveldd3, prace, snsf, transport
Antiferromagnetic spin canting and magnetoelectric multipoles in h-YMnO₃

We present our resonant X-ray diffraction work to study the antiferromagnetic spin canting perpendicular to the hexagonal planes of the archetypal type-I multiferroic YMnO₃. We find the x-ray diffraction spectral shape at the Mn L2,3 edges change as a function of temperature below TN for this material. Using a combination of phenomenological arguments and computations using the DFT-based FDMNES code, we attribute the difference spectra to be a result of interference of scattered amplitudes from the canted magnetic dipole and higher-order magnetoelectric multipoles.

Tags: dft, experimental, marvel, snsf
Vertex function compliant with the Ward identity for quasiparticle self-consistent calculations beyond GW

We extend the quasiparticle self-consistent approach beyond the GW approximation by using a range-separated vertex function. The developed approach yields band gaps, dielectric constants, and band positions with an accuracy similar to highest-level electronic-structure calculations without exceeding the cost of regular quasiparticle self-consistent GW. We introduce an exchange-correlation kernel that accounts for the vertex over the full spatial range. In the long range it complies with the Ward identity, while it is approximated through the adiabatic local density functional in the short range. In this approach, the renormalization factor is balanced and the higher-order diagrams are effectively taken into account.

Tags: electronic-bands, electronic-structure, gw, ionization-potential, many-body-perturbation-theory, vertex
Atomistic simulation of carbohydrate-protein complex formation: Hevein-32 domain

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

Tags: carbohydrate-protein-interactions, docking-by-dynamics, molecular-dynamics-simulation
An overview of the spin dynamics of antiferromagnetic Mn₅Si₃

The metallic compound Mn5Si3 hosts a series of antiferromagnetic phases that can be controlled by external stimuli, such as temperature and magnetic field. In this work, we investigate the spin-excitation spectrum of bulk Mn5Si3 by combining inelastic neutron scattering measurements and density functional theory calculations. We study the evolution of the dynamical response under external parameters and demonstrate that the spin dynamics of each phase is robust against any combination of temperature and magnetic field. In particular, the high-energy spin dynamics is very characteristic of the different phases consisting of either spin waves or broad fluctuation patterns. This data set contains the data relevant to performing the spin dynamics simulations with the Spirit code, the spin-wave calculations with the SWIS code, and the neutron scattering experimental data.

Tags: antiferromagnetism, frustration, inelastic-neutron-scattering, intersect, marvel, noncollinear-magnetism, spin-waves
Oxidation states, Thouless' pumps, and nontrivial ionic transport in nonstoichiometric electrolytes

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

Tags: charge-transport, max, solvation, thouless-pump, transport-properties
Low-temperature crystallography and vibrational properties of rozenite (FeSO₄·4H₂O), a candidate mineral component of the polyhydrated sulfate deposits on Mars

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

Tags: dftu, infrared, mars, phonons, raman, spectroscopy
Structure and energetics of dye-sensitized NiO interfaces in water from ab-initio MD and large-scale GW calculations

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

Tags: ab-initio, c343nio-interface, energy-level-alignment, gw, molecular-dynamics-simulation, nio, p-type-dssc
Screening of low-friction two-dimensional materials from high-throughput calculations using frictional figure of merit

Two-dimensional materials are excellent lubricants with inherent advantages. However, superlubricity has only been reported in a few of them. It is a regret that other promising 2D materials with different physical properties cannot be discovered and applied in production so that energy consumption can be greatly reduced. Here we carry out high-throughput calculations for 1475 two-dimensional materials and screen for low-friction ones. To set a standard, we propose, for the first time, a geometry-independent frictional figure of merit based on the condition for stick-slip transition and our theory of Moiré friction. For the efficient calculation of this figure of merit, an innovative approach is developed based on an improved registry index model. Through the calculation, 340 materials are found to have a figure of merit lower than 10-3. Eventually, a small set of 21 materials with a figure of merit lower than 10-4 are screened out within them. These materials can provide diversified choices for applications. In addition, the efficient computational approach demonstrated in this work can be used to study other stacking-dependent properties.

Tags: high-throughput-calculation, low-friction-materials, moire-patterns, tribology, two-dimensional-materials
Ultrasonic spray coating of polyethylenimine (ethoxylated) as electron injection and transport layer for organic light emitting diodes

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

Tags: electron-injection-and-transport-layer, experimental, organic-light-emitting-diodes, polyethylenimine-ethoxylated, printing-technique, ultrasonic-spray-coating