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[Display omitted] Developing high storage capacity of lithium-ion batteries (LIBs) by applying novel anodes based on nanostructures has been allocated to extensive research. Although, SP2-hybrid carbon nanostructures exhibit a low storage capacity, a two-dimensional (2D) graphyne (Gy) monolayer is proved to be an efficient electrode material due to its large surface area and significant mechanical and chemical properties. Herein, a derivative of Gy called α-graphyne nanotube (αGyNT) is proposed as the anode material of LIBs, in which the adsorption of lithium (Li) on Gy nanobelt (GyNB) (one-segment) and short open-ended GyNTs with different lengths are modeled by implementing of ab initio first-principles calculations. Lithium diffusion behaviors inside and outside of GyNTs has been investigated by ab initio molecular dynamics (ABMD) to calculate open-circuit voltage. The results reveal that Li adsorption energies of short αGyNTs have no regular oscillatory dependence on the number of segments along the tube axis (length of the tubes). Furthermore, the largest storage capacity of C 4 Li 4 (1273.75 mAh/g) was obtained for (4, 4) αGyNTs, which demonstrate better storage capacity compared to single/multiple graphyne nanostructures. The curvature of αGyNTs can enhance the diffusion of Li atoms and leads to promote storage capacities, which suggest these anode materials improve LIBs's performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Energy barrier values set for vacancy-assisted solute migration in Al alloys is given. • Results explain why the main age-hardenable alloy families are Al-Cu-Mg & Al-Zn-Mg. • Synergy between Mg & Ag explain why Ag enhance alloys' mechanical response greatly. • The energy values can be used to aid kMC simulations for large-scale alloy models. In this work, a consistent and accurate set of energy barrier values for the migration process, assisted by a vacancy, of atoms of different chemical elements belonging to the two most relevant families of age-hardenable Al-Cu and Al-Zn-based alloys is given. These values were calculated using the Nudged Elastic Band method within the Density Functional Theory framework for a vacancy diffusing in simple configurations of solute atoms, specifically the main alloying elements Cu and Zn involving a single solute atom or more complex configurations, such as pairs of elements of the same or different chemical species. In both cases, in our calculations, the presence of Mg and/or Ag solute atoms is also considered. The results obtained are analyzed in terms of the energetic interaction among vacancies and the different solute atoms. The advantage of having a set of vacancy diffusion energy barrier values calculated under the same criteria is that it can be used as reliable input parameters for future kinetic Monte Carlo simulations to study the precipitation kinetics in a wide type of age-hardenable alloys. [ABSTRACT FROM AUTHOR]

Corrosion has a wide impact on society, causing catastrophic damage to structurally engineered components. An emerging class of corrosion-resistant materials are high-entropy alloys. However, high-entropy alloys live in high-dimensional composition and configuration space, making materials designs via experimental trial-and-error or brute-force ab initio calculations almost impossible. Here we develop a physics-informed machine-learning framework to identify corrosion-resistant high-entropy alloys. Three metrics are used to evaluate the corrosion resistance, including single-phase formability, surface energy and the compactness of oxide films formed on an alloy surface evaluated by Pilling–Bedworth ratios. We used random forest models to predict the single-phase formability, trained on an experimental dataset. Machine learning inter-atomic potentials were employed to calculate surface energies and Pilling–Bedworth ratios, which are trained on first-principles data fast sampled using embedded atom models. A combination of random forest models and high-fidelity machine learning potentials represents the first of its kind to relate chemical compositions to corrosion resistance of high-entropy alloys, paving the way for automatic design of materials with superior corrosion protection. This framework was demonstrated on AlCrFeCoNi high-entropy alloys and we identified composition regions with high corrosion resistance from a wide range of compositions. Machine learning predicted lattice constants and surface energies are consistent with values by first-principles calculations. The predicted single-phase formability and corrosion-resistant compositions of AlCrFeCoNi agree well with experiments. This framework provides a computationally efficient approach to navigate high-dimensional composition space of high-entropy alloys. It is general in its application and applicable to other complex materials, enabling high-throughput screening of material candidates and potentially accelerating the iteration of integrated computational materials engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

Metal fluorides are ionic compounds with intriguing properties and a wide range of industrial and technological applications. In this paper, we present the results of an extensive first-principles study of the electronic band structure of nineteen mono-, di-, and tri-fluorides. Four approaches are employed in this study: LDA, pseudopotential and all-electron modified Becke–Johnson (mBJLDA@PP and mBJLDA@AE) potentials, and Yukawa Screened Hybrid Functional (YS-PBE0). The mBJLDA and YS-PBE0 band gaps are in good overall agreement with the available G 0 W 0 results and experimental data, which ensures the reliability of the provided predictions for systems where accurate band gaps are lacking. The LDA and YS-PBE0 upper valence band (UVB) widths are very close to each other, and these results are, in general, slightly smaller than the G 0 W 0 results and experimental data. It is shown that the band gap and UVB width vary with F F distance, and distinct trends are identified. The LDA density of states of the UVB for the alkali and alkaline-earth fluorides are analyzed and compared to the available XPS and XES spectra. It is found that the LDA approach provides accurate results for peak intensities as well as satellite peak positions relative to the main peak. A strong correlation is demonstrated between the adopted crystal structures of the considered fluorides and their bond ionicity. • Four approaches are used to study the electronic structure of 19 metal-fluorides. • For several of the fluorides considered, reliable predictions have been made. • Band gaps and upper valence band widths are found to exhibit clear trends. • The bonding mechanisms of fluorides are discussed in detail. • A correlation is established between bond ionicity and crystal structure. [ABSTRACT FROM AUTHOR]

The investigation of interface residual stress and interface elastic moduli tensors plays a crucial role in enhancing the conventional theory of elasticity. These considerations allow us to account for size effects and eliminate nonphysical singularities near defects. The primary objective of this study is to comprehensively calculate interface energy, residual stress components, and interface elastic moduli tensors for various interfaces between non-magnetic fcc metals using density functional theory (DFT). We achieve this by performing ab initio DFT calculations to determine the interface energies for different coherent interfaces among these metals. Subsequently, these energies are integrated into the corresponding formulations within surface/interface elasticity theory, enabling us to derive the residual stress and interface elastic constants specific to the target interface. Additionally, we identify and analyze unstable interfaces that exhibit phase transformations, cleavage, and mixing instabilities. Validation is also made with the available laboratory experimental results. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, the electronic, optical, and photovoltaic properties of the two double perovskites were determined, represented, and interpreted using ab initio calculations. The calculations were based on the generalized gradient of Perdew, Burke and Ernzerhof and Tran-Blaha-modified Becke-Johnson approximations within the framework of density functional theory. Quantities that predict the use of dual perovskites in photovoltaic, such as external quantum efficiency, open-circuit voltage and short-circuit current were calculated. These quantities were calculated based on optical properties, in particular the dielectric function, reflectivity, and absorption coefficient. Based on the electronic properties, the gap values obtained with TB-mBJ are 2.13 eV and 1.65 eV, while those obtained with GGA-PBE are 1.48 eV and 1.07 eV for Cs 2 AgBiBr 6 and Cs 2 AgSbBr 6 , respectively. The variations in external quantum efficiency and optical absorption coefficient show a strong evolution around the range of energies making up the visible spectrum. This makes them promising materials for the photovoltaic industry. We will apply various pressure values, ranging from 0 to 30GPa, to our structures in order to gain an improved comprehension of the effect of pressure on the energy loss function. [ABSTRACT FROM AUTHOR]

[Display omitted] Tetragonal ratio (c / a) is a critical structural parameter that heavily decides plenty of performances of tetragonal martensitic materials. Nevertheless, the knowledge about c/a remains limited and there is still no definitive strategy to tailor it. In this work, the machine learning method, combined with high-throughput ab-initio calculation, was introduced as an attempt to investigate c/a. After training, a high-precision random forest model of predicting c / a was established. Combining a five-step descriptor screening and visualization analyses, the most pertinent parameters deciding c / a , i.e. , mean melting point ( T ¯ M) and mean volume ( V ¯ ) of constituent elements, were identified. Furthermore, a simple relation between c/a and these two parameters, i.e. , c / a = m T ¯ M / V ¯ + b where the m and b are constants, was proposed. Surprisingly, this relation exhibits an exceptional generalization performance in a wide range of untrained materials. This work is expected to provide an explicit, efficient and general route to tailor c/a and hence promote the design of advanced martensitic materials. [ABSTRACT FROM AUTHOR]

Assembling two dimensional (2D) materials in vertical heterostructures is one of the main techniques for tuning electronic and optical properties. In most cases, known as van der Waals heterostructures (vdWHs), the interlayer distances are larger than typical covalent bond lengths resulting in weak interlayer interactions. It has been shown that reducing the distance between the layers can significantly alter the properties of separated layers, which is not so noticeable in vdWHs and thus creates a new platform for controlling the physical properties of 2D materials. Motivated by enhanced properties of 2D vertical heterostructures, employing ab-initio calculations based on density functional theory we examined CdO/SnC systems in four different configurations. Our results reveal that in spite of thermodynamic and mechanical stabilities of all considered structures, according to the calculated phonon frequencies, only the structure formed by placing the Sn atom on the O atom and the C atom on the Cd atom is dynamically stable at zero temperature. This structure has an interlayer distance of 2.52 Å which is smaller than the interlayer distance in typical vdWHs. We investigated the electronic and optical properties of this dynamically stable structure utilizing GW approximation and solving Bethe–Salpeter equation. Unlike the monolayer CdO which possesses a single optical absorption peak close to the red light energy, the considered CdO/SnC structure has an optical band gap of 1.14 eV, and it can absorb 13% of incident light in the blue light region. [ABSTRACT FROM AUTHOR]

[Display omitted] • Genetic algorithm optimizes interatomic potentials for cubic ZrO 2 and YSZ. • Developed potentials sufficiently reproduce energy, force, and stress from DFT. • The potentials enable fast and accurate evaluation of material properties of YSZ. Yttria stabilized zirconia (YSZ) is an important engineering ceramic oxide used for various applications, including solid electrolytes in solid oxide fuel cells due to its high ionic conductivity. Accurate and computationally inexpensive interatomic potentials for cubic ZrO 2 and YSZ are required to accommodate the large number of defect configurations originating from high concentrations of Y and oxygen vacancies and to statistically understand their properties in realistic time. In this study, a genetic algorithm has been used to optimize empirical interatomic potential parameters for cubic ZrO 2 and 10Y 2 O 3 mol% YSZ using energies, forces acting on atoms, and stresses generated by ab initio calculations as training data. The optimized potentials reproduce the structural, mechanical, and thermal properties as well as the ionic conduction properties more accurately than previously reported empirical interatomic potentials. The developed potentials will be useful for a statistical characterization of YSZ properties, combined with more accurate ab initio calculations. [ABSTRACT FROM AUTHOR]

The trajectory along the diffusion path is determined by structure repetitions, or images, within the Nudged Elastic Band methodology. In the literature using a single image, among the initial and final position of the vacancy site, is well accepted to determine the transition state, and hence, the enthalpy of migration to model diffusion within aluminium. Scaling the number of evolving images, in the Nudged Elastic Band methodology, is performed for the first time to our knowledge, to determine transition states for the diffusion of magnesium in face centred cubic aluminium. Since a single image locates the transition state away from the expected middle place, along the diffusion path. With an odd number of evolving images is possible to clearly place the saddle point exactly halfway, in between extremal positions, as the enthalpy of migration converges its magnitude. Adjusting the number of evolving images consolidates then a scheme to accurately determine transition states, within the methodology to compute macroscopic diffusion factors, and the results also demonstrate that single image calculations provide a coarse result for diffusion parameters, meanwhile, the converged number of images locates the Arrhenius plot in good agreement with previous ab-initio calculations and experimental measurements. [Display omitted] [ABSTRACT FROM AUTHOR]

We developed and validated an accurate inter-atomic potential for molecular dynamics simulation in cubic silicon carbide (3C-SiC) using a deep learning framework combined with smooth Ziegler–Biersack–Littmark (ZBL) screened nuclear repulsion potential interpolation. Comparisons of multiple important properties were made between the deep-learning potential and existing analytical potentials which are most commonly used in molecular dynamics simulations of 3C-SiC. Not only for equilibrium properties but also for significant properties of radiation damage such as defect formation energies and threshold displacement energies, our deep-learning potential gave closer predictions to the DFT criterion than analytical potentials. The deep-learning potential framework solved the long-standing dilemma that traditional empirical potentials currently applied in 3C-SiC radiation damage simulations gave large disparities with each other and were inconsistent with ab initio calculations. A more realistic depiction of the primary irradiation damage process in 3C-SiC can be given and the accuracy of classical molecular dynamics simulation for cubic silicon carbide can be expected to the level of quantum mechanics. [Display omitted] [ABSTRACT FROM AUTHOR]

This study employs density functional theory (DFT) and density functional tight-binding theory (DFTB) to determine the adsorption properties of carbon dioxide (CO 2), methane (CH 4), and dihydrogen (H 2) in carbophenes functionalized with carboxyl (COOH), amine (NH 2), nitro (NO 2), and hydroxyl (OH) groups. We demonstrate that carbophenes are promising candidates as adsorbents for these gasses. Carbophenes have larger CO 2 and CH 4 adsorption energies than other next-generation solid-state capture materials. Yet, the low predicted desorption temperatures mean they can be beneficial as air scrubbers in confined spaces. Functionalized carbophenes have H 2 adsorption energies usually observed in metal-containing materials. Further, the predicted desorption temperatures of H 2 from carbophenes lie within the DOE Technical Targets for Onboard Hydrogen Storage for Light-Duty Vehicles (DOEHST) operating temperature range. The possibility of tailoring the degree of functionalization in combination with selecting sufficiently open carbophene structures that allow for multiple strong interactions without steric hindrance (crowding) effects, added to the multiplicity of possible functional groups alone or in combination, suggests that these very light materials can be ideal adsorbates for many gases. Tailoring the design to specific adsorption or separation needs would require extensive combinatorial investigations. • CO 2 and CH 4 adsorption energies larger than other solid-state capture materials. • CO 2 and CH 4 desorption temperatures mean they may be beneficial in confined spaces. • H 2 adsorption energies usually observed in metal-containing materials. • Desorption temperatures of H 2 lie within the government indicated ranges. [ABSTRACT FROM AUTHOR]

[Display omitted] • MX 2 exhibits an appreciable change in bond length and angle in the vdW environment, which has a notable influence over the in-plane/out-of-plane atomic orbital overlap. • Chalcogen specifications in the middle layer of SnS 2 /MX 2 /SnS 2 significantly influence the interlayer interaction and subsequent interlayer charge transfer. • Intrinsic strain in the middle layer of SnS 2 /MX 2 /SnS 2 and interlayer charge transfer leads to significant energy band gap reductions in the vdW tri-layers compared to 3L-SnS 2. • The vdW 3L demonstrates metallic, semi-metallic, and semiconducting energy band structures based on the MX 2 specifications and interlayer stacking. Recently, the van der Waals (vdW) heterostructure design has gained paramount importance for realizing artificial two-dimensional (2D) material systems with tunable electronic/opto-electronic properties for different technological applications. Driven by this paradigm, in this work, a detailed theoretical analysis has been performed on the structural and electronic properties of different tri-layer van der Waals (vdW) heterostructure of SnS 2 /MX 2 /SnS 2 (M = Mo, W; X = S, Se, Te) via density functional theory(DFT) based Ab-initio calculation. Moreover, for individual vdW tri-layers, two characteristics of interlayer stacking configurations corresponding to natural stacking configurations of tri-layer SnS 2 and MX 2 have been considered. The structural properties are evaluated from the interlayer distance, bond angle, bond length, electrostatic difference potential, electron difference density, and Mulliken charge distributions. The electronic properties of different vdW tri-layers are assessed from the interlayer charge transfer, energy band structures, and the density of states profiles, which are quantified from the energy bandgap and effective masses, which are finally compared and benchmarked with homogenous tri-layer SnS 2. It has been observed that the chalcogen specification of the middle layer predominantly influences the interlayer interaction and thereby, structural/electronic properties of vdW tri-layers. The vdW tri-layers demonstrate metallic, semi-metallic, and semiconducting energy band structures (bandgap ranging from 0.138 to 0.729 eV, electron effective mass ranging from 0.286/0.286 m 0 to 1.299/0.342 m 0 , hole effective mass ranging from 0.216/0.216 m 0 to 2.825/2.927 m 0) based on the middle layer MX 2 specifications and stacking orientations. [ABSTRACT FROM AUTHOR]

[Display omitted] Using the crystal structure prediction combined with element substitution, several new layered Li x (B y C 1-y) 2 structures with 5-, 6-, and 8-membered BC/C rings are proposed. Phonon calculations and ab initio molecular dynamics simulations confirm that they are all dynamically and thermodynamically stable. To investigate the effect of boron content on electrochemical properties in these layered Li x (B y C 1-y) 2 (y = 0, 0.1, 0.2, 0.3, and 0.4) anode materials, we study their theoretical voltages, capacities, and Li diffusion mechanism by the first-principles calculations. Our calculated results show that high boron content structures have high theoretical capacities within the 0–2 V potential window. Li 0.8 (B 0.3 C 0.7) 2 has the highest capacity among them, with a capacity of 557 mAh/g, which is about 1.5 times higher than that of graphite (372 mAh/g). While they also have high average voltages, which is detrimental to the open circuit voltage of cells. Moreover, calculated ionic diffusions also show that boron carbon structures have higher activation barriers (>0.48 eV) than that of pure carbon (∼0.36 eV), indicating a poorer Li diffusion. However, the analysis of electronic properties reveals that these 5-, 6-, and 8-membered-ring Li x (B y C 1-y) 2 are all metallic, which suggests they may all have good electronic conductivity. Their calculated volume changes are all less than 6.73 %, indicating they will have excellent structural stability during the charge/discharge process. Our results broaden the current understanding of non-hexagonal boron carbides and provide guidelines for the future design of new boron carbides as anode materials. [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, we have investigated the structures and phase transitions of the Ca-P system under high pressure using the first-principles calculation method combined with the CALYPSO structural searching technique. We discovered new phases with the chemometrics of Ca x P y (x / y = 1/1, 1/2, 3/2,2/1) and found that Ca 3 P 2 and Ca 2 P decompose into elemental solid calcium and phosphorus at external pressures of 459 GPa and 478 GPa, respectively. This phenomenon contradicts the common knowledge that pressure usually leads to denser and more stable compound structures. As pressure increases, the Δ PV term of the compound exhibits an upward trend, which serves as the principal cause of Ca 3 P 2 decomposition. We have delved into the electronic properties of Ca 3 P 2 , encompassing Bader charge, Madelung energy, band structures, Electron Localization Function (ELF), and ICOHP. The findings give evidence that the abatement of inter-ionic interaction, triggered by pressure, constitutes the foremost factor inducing Ca-P compounds composition into solid elements. Our research elucidates how high pressure regulates Ca-P compounds behavior and electronic properties, and offers valuable insight into the behavioral transformations of other alkaline-earth metal phosphides under high pressure. [ABSTRACT FROM AUTHOR]

We calculated electronic structure of Ce 2 Rh 3 Ga 9 , Ce 2 Ru 3 Ga 9 , La 2 Ir 3 Al 9 and Ce 2 Ir 3 Al 9 compounds and we found that Ce 2 Ir 3 Al 9 may exhibit strong topological insulator state according to Z 2 index estimation based on parity algorithm and shape of band structure near Fermi level. The same algorithm shows strong topological insulator state for La 2 Ir 3 Al 9 and Ce 2 Rh 3 Ga 9 compounds, but their band structure near Fermi level is more like semimetallic one. Ce 2 Ru 3 Ga 9 is a normal metal. Our calculations show no magnetic ordering for studied compounds. We also measured the XPS (X-ray Photoelectron Spectroscopy) spectra for these materials, and compared the valence band with simulated spectra, where good agreement was found. Core level states were also investigated and compared with Mulliken population analysis results. According to our measurements and calculations, the highest Ce valence is observed for Ce 2 Ir 3 Al 9 whereas for Ce 2 Rh 3 Ga 9 and Ce 2 Ru 3 Ga 9 the Ce valence is smaller. Hybridization between conduction electrons and 4 f states is very small, and for Ce 2 Ru 3 Ga 9 essentially negligible. [Display omitted] • The first electronic structure calculations with FPLO method of Ce 2 Rh 3 Ga 9 , Ce 2 Ru 3 Ga 9 , La 2 Ir 3 Al 9 and Ce 2 Ir 3 Al 9 have been reported. • The calculations show, that in the case of Ce 2 Ir 3 Al 9 the hour glass-like structure is visible at Γ point, but this structure is visible slightly above the ϵ F. • We found that Ce 2 Ir 3 Al 9 may exhibit strong topological insulator state. • Our calculations show no magnetic ordering for studied compounds. • Moreover, we also found that hybridization of 4 f and conduction electrons is small for Ce 2 Ir 3 Al 9 and Ce 2 Rh 3 Ga 9 and close to zero for Ce 2 Ru 3 Ga 9. [ABSTRACT FROM AUTHOR]

• The mechanism of selective fluoride ion conduction in LaOF was investigated. • Formation of an F Frenkel pair was favored over that of an O Frenkel pair. • Fluoride ions diffused dominantly via an interstitialcy mechanism in LaOF. • An interstitialcy mechanism occurred when F and O were ordered along [0 0 1]. Ionic conduction in LaOF was investigated by density functional theory-based first-principles calculations. The origin and microscopic mechanism of selective fluoride ion conduction in LaOF were investigated by evaluating the formation energy of the Frenkel pair and by performing ab initio molecular dynamics (MD) simulations for both tetragonal (anion order along the [0 0 1] direction) and rhombohedral (anion order along the [1 1 1] direction) structures experimentally obtained in LaO 1− x F 1+2 x. In both structures, the formation of an F Frenkel pair was energetically favored over that of an O Frenkel pair, and the F Frenkel pair predominantly contributed to the conduction of fluoride ions. From the trajectory of MD simulations with an F or O Frenkel pair in the two structures, it was found that fluoride ion conduction mainly occurred via an interstitialcy mechanism. This fluoride ion migration occurred only in the tetragonal structure along the (0 0 1) plane. This observation was further confirmed by migration barriers evaluated by the climbing-image nudged elastic band method. The results suggested the possibility of the enhancement of ionic conductivity by controlling the anion ordering in mixed anion compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Methodology of spin-polarised ab-initio calculations is revisited. • Ferromagnetic HoN requires an unusually high number of unoccupied electronic states. • Electronic structure and crystal characteristics depend on magnetisation. • Capturing the experimental magnetic moment requires a large simulation cell. • Preferred spin distribution in rare-earth nitride HoN is predicted. Rare-earth mononitrides such as HoN exhibit a wide range of useful properties leading to potential applications as magnetic semiconductors, spintronic half-metals, or magnetocaloric refrigerants in hydrogen liquefaction systems. First-principle calculations of electronic structures and related properties of such materials should correctly reproduce their magnetic moment. First, we identify the unusually high number of unoccupied electronic states which guarantees that the energy minimum identified is the global one. Second, we develop a method which allows the experimentally relevant magnetisation to constitute an energy minimum, emphasising the favourable distribution of the spins in an exceptionally large simulation cell. Third, we examine the dependence of selected HoN characteristics on the cell size and on the magnetisation. The results provide a theoretical insight into the spin structure of rare-earth nitrides and allow one to use the correct methodology of similar calculations of properties of strongly correlated materials. [ABSTRACT FROM AUTHOR]

Molecular statics/dynamics (MS/MD) based on empirical interatomic potentials (IAPs) is an effective means for conducting grain boundary (GB) related studies. The accuracy of these MS/MD simulations, however, can be greatly affected by the IAP used. Unfortunately, the large discrepancies between the ab-initio values make it difficult to evaluate, improve and further develop IAPs. Motivated by this issue, in the present work we perform a systematic investigation of 〈100〉 and 〈110〉 symmetric tilt GBs in tungsten (W) via atomistic simulations, including the stable structure, GB energy, work of separation, excess volume, and vacancy formation energy. We here use a two-step relaxation process, initially obtaining the candidate structures from MS and then performing DFT validation of these structures to determine the ground state structure, where six empirical IAPs and four exchange–correlation (xc) functionals are used. And the step-like feature is revealed that can be used to reduce the cost of time-consuming optimization processes. Taking the results yielded by PBEsol xc-functional as a benchmark, it is shown that for the same xc-functional, the relative errors of GB energy and work of separation are almost identical, independent of the GB character. The performance of six typical empirical IAPs considered for W is also evaluated by comparing it with the DFT data. The quantities chosen for the comparison include the structure and energetic properties of GBs, as mentioned before. We demonstrate that these empirical IAPs tend to better describe only part of the properties of GBs; for example, some IAPs can predict the energetic properties well, while others can better describe the structure. This suggests that a fully reliable description of GBs remains an elusive objective, requiring further efforts in the development and optimization of the IAP. [ABSTRACT FROM AUTHOR]

Coinage metals doped 1T´ WS 2 are explored as a cathode electrocatalysts material using ab initio calculation in acidic medium Fuel Cell. Oxygen Reduction Reaction (ORR) and Hydrogen Evolution Reaction(HER) were studied to observe bi-functional activity of each doped system. [Display omitted] The electrocatalytic activities of Cu, Ag and Au doped 1T′ WS 2 as electrocatalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in acidic medium are explored by means of first principles calculations. The stability of these doped systems are inspected in terms of formation energy and charge transfer analysis upon doping. Highest amount of charge transfer towards the dopant is observed for systems with lowest formation energy. For all the doped systems, charge is transferred to the dopant that substitutes the anionic S atom validating the doping scheme and stability of the doped systems. ORR proceeds only via the energetically efficient four electron pathway on Cu doped 1T′ WS 2 with a monotonically exothermic free energy profile. In the case of Ag and Au doped structures, ORR occurs competitively via both two and four electron pathways due to the marginal free energy difference in the 2nd protonation step between these two pathways and produces both H 2 O or H 2 O 2 competitively as the end product. Study of the effect of electrode potential variation on the free energy profiles reveals the overpotential for ORR on Cu, Ag and Au doped 1T′ WS 2 to be 0.85 V, 0.80 V and 0.66 V respectively via the four electron pathway. Proneness of Cu doped 1T′ WS 2 towards only the four electron pathway and low overpotential for ORR makes it the promising cathode electrocatalyst for ORR among the considered systems. Further study of the HER activity of Cu, Ag and Au doped 1T′ WS 2 reveals the Gibbs free energy of H+ ion adsorption on Cu doped 1T′ WS 2, Ag doped 1T′ WS 2 and Au doped 1T′ WS 2 to be −0.14 eV, −0.17 eV and 0.18 eV respectively indicating high efficiency of those system towards HER in acidic medium. [ABSTRACT FROM AUTHOR]

• The perovskite HoMnO 3 crystal structures are studied in this work. • The simulations using Quantum Espresso are applied and discussed. • The DFT method is applied to understand its properties. • The elastic properties are investigated. • The mechanical behavior is deduced. The structural and elastic properties of the oxide perovskite HoMnO 3 have been investigated by density-functional theory (DFT) implemented on the Quantum ESPRESSO code for the hexagonal, orthorhombic, rhombohedral and cubic crystal structures in the non-magnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) configurations. The results show that all these compounds are thermodynamically stable, the hexagonal and the orthorhombic being the most stables in agreement with experimental results. The calculated bulk modulus, B, is about 168.5 ± 1.0 GPa and 178.9 ± 1.0 GPa for hexagonal structure in FM and configurations, respectively, and 188.7 ± 0.6 GPa and 175.6 ± 2.1GPa for orthorhombic structure in FM and AFM configurations, respectively. These values and those of the elastic constants C ij in the present work are comparable to values recently obtained with DFT calculations and experimentally for other perovskites RMnO 3 (R = Eu, Gd, Tb and Dy). The calculated Poisson's ratio is about 0.19; 0.27; 0.23 and 0.3 for hexagonal, orthorhombic, rhombohedral and cubic structure, respectively. The calculated Pugh's ratio is about 1.30; 1.77–1.98; 1.54–1.60 and 2.11, respectively. These results show that the perovskite HoMnO 3 tends to be brittle in hexagonal phase and ductile in cubic phase. In the orthorhombic or rhombohedral phase, it is near brittle-ductile boarder line. [ABSTRACT FROM AUTHOR]

[Display omitted] In the process of heat treatment at high temperature, A 2 B type intermetallic compound Fe 2 Mo can precipitate out in the martensitic heat-resistant steel. When the martensitic heat-resistant steel is used in high concentration alkali solution of 7 mol/L, the Fe 2 Mo Laves phase can dissolve. Meantime, the dissolution behaviors of different shapes of Fe 2 Mo Laves phase are also distinct. However, there is still no effective micro-mechanism to explain the dissolution behaviors of Fe2Mo Laves phase. Thus, in this work, the adsorption behavior of OH− on Fe 2 Mo(0 0 1), (0 1 0), (1 1 0) and (1 1 2) surfaces was simulated by ab initio calculations. And corresponding electronic effects were comparatively analyzed, the results of which show that the outmost surface of Fe 2 Mo changed significantly before and after adsorption, demonstrating that the Fe 2 Mo surface can be influenced by OH−. The results of adsorption energy, Mulliken population, density of states and electronic local function indicate that the Fe 2 Mo(0 0 1) surface has a greater adsorption trend, and the OH−/Fe 2 Mo(0 0 1)-b configuration has the largest adsorption energy. Electrons transfer from OH− to the Fe 2 Mo surface, and the adsorption type is chemisorption. The results provide a theoretical basis for studying the selective dissolution of Fe 2 Mo Laves phase in strong alkali solution. [ABSTRACT FROM AUTHOR]

Graphical abstract The maximum absorption exists in the visible light region for all the phases studied; making In-doped AlFeO 3 suitable for energy harvesting applications. Highlights • Electron effective mass is smaller than that of holes for Al 1−x In x FeO 3. • Effective electron mass tensor is fairly isotropic; hole mass is not so. • High dielectric-constants of Al 1−x In x FeO 3 indicate promise for charge separation. • Reflectivity peaks for all the phases is found near IR and UV region. • Absorption-spectra indicate relevance for visible light harvesting. Abstract Electronic and optical properties of AlFeO 3 and Al 1−x In x FeO 3 (x = 0.25, 0.5, 0.75) are studied using ab-initio calculations. Electronic structure in the vicinity of the conduction band minimum (CBM) and valence band maximum (VBM), the effective masses of holes and electrons at the gamma point are calculated. The calculated effective masses of electrons is smaller than that of holes (m c1 ⊥, m c1 ‖ (m e *) < m v1 ⊥, m v1 ‖, m v2 ⊥, m v2 ‖ (m h *)), for all values of x; this is expected to contribute to the desirable photocatalytic performance. Effective mass tensor for electrons is found to be isotropic (unlike holes). The optical constants such as static dielectric constant, refractive index, extinction coefficient and absorption coefficient are comparable with that Si. The maximum absorption exists in the visible light region for all the phases studied; making In-doped AlFeO 3 suitable for energy harvesting applications. We noted from our previous work (Sudha Priyanga and Thomas, 2018) that the computed band gap values could be underestimated by as large as ∼0.5 eV. Even so, the reported phases would be relevant for light harvesting. [ABSTRACT FROM AUTHOR]

• The calculations of the structural, electronic, and magnetic properties of new full Heusler alloys Co 2 ZrZ (Z = Pb, Bi, As) were performed. • The most stable structure of these compounds is Cu 2 MnAl with the L2 1 structure. • The majority and minority of DOS show that the Co 2 ZrPb compound has half-metallic nature with a band gap of 0.33 eV. • The band structure and DOS of Co 2 ZrBi and Co 2 ZrAs compounds exhibit ferromagnetic metallic nature of alloys. In this paper, the calculations of the structural, electronic, and magnetic properties of new full Heusler Co 2 ZrZ (Z = Pb, Bi, As) alloys were investigated within the framework of the density functional theory (DFT). Calculations were performed using the Quantum-Espresso package and ultrasoft pseudopotential, based on generalized-gradient approximation (GGA) as the exchange–correlation potential. Using ab initio calculations, properties such as equilibrium lattice constants (a 0), bulk modulus (B), electronic band structures, majority and minority of density of states (DOS), as well as the total and atomic magnetic moments of these new compounds were calculated. The results show that the most stable structure of these compounds is the Cu 2 MnAl phase with a L2 1 crystal structure. The calculation of the electronic band structure and the majority and minority of DOS show that the Co 2 ZrPb compound has half-metallic nature with a band gap of 0.33eV. However, based on the band structure and total and partial DOS, the Co 2 ZrBi and Co 2 ZrAs compounds exhibit ferromagnetic metallic nature. In addition, the calculation of the magnetic properties indicates that the Co 2 ZrPb has a total magnetic moment of 2µ B , which follows the Slater-Pauling (SP) rule. [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-diffusion coefficients for the fastest mechanisms are evaluated. • Ti diffuses along the c axis faster than in the perpendicular direction. • Self-diffusion is dominated by Ti on its own sublattice. • Doping with transition metals reduces the Ti diffusion rate. The mechanisms of the Ti and Si self-diffusion in the Ti 5 Si 3 compound are investigated by using the projector augmented-wave method within the density functional theory. The migration and activation energies for Ti and Si atoms were calculated for both vacancy and interstitial mechanisms. It is shown that the smallest migration energy of Ti atom corresponds to the interstitial mechanism, whereas it is by 0.08 eV lower for the Si own-sublattice mechanism than for interstitial one. The concentration of initial point defects within canonical formalism is calculated and the most preferred defects are determined. The temperature-dependent self-diffusion coefficients along two crystallographic directions are calculated. It is shown that Ti atom diffuses faster than Si one. The influence of metals of IVB–VIIB groups on the Ti migration energy is estimated. It is shown that almost all considered impurities increase the migration energy and can lead to a decrease in Ti diffusivity in Ti 5 Si 3. [ABSTRACT FROM AUTHOR]

Pt 2 Ga and Pd 2 Ga monolayers are high-efficiency multifunctional electrocatalytic materials. [Display omitted] • We theoretically report two novel 2D electrocatalysts with low Pt loading. • The HER activity of Pd 2 Ga monolayer is higher than that of currently commercialized Pt. • Pt 2 Ga monolayer possesses extremely lower overpotentials for OER and ORR, which can act as high-performance multifunctional electrocatalysts. • We provide an effective guidance for the rational design of multifunctional electrocatalysts. Developing multifunctional electrocatalysts with high performance for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is still a challenging task. In this work, the electrocatalytic activities of Pt 2 Ga and Pd 2 Ga monolayers are systematically investigated based on first-principles calculations. The high dynamic and thermal stabilities of Pt 2 Ga and Pd 2 Ga monolayers are confirmed by phonon dispersion calculations and ab initio molecular dynamics (AIMD) simulations, respectively. In addition, the Pd 2 Ga free energy for H adsorption is predicted to be −0.03 eV, implying its extremely high activity for HER. Furthermore, the Pt 2 Ga overpotential for OER and ORR are estimated to be 0.48 and 0.42 V, correspondingly, indicating its high catalytic performance. This work provides adequate guidance for designing multifunctional electrocatalysts with high performance for OER, ORR and HER. [ABSTRACT FROM AUTHOR]

A design map in regard to the generalized-stacking fault (GSF) energy is plotted for Ti 5 Si 3 (Ti 60 Si 36 ) alloying with 12 ternary elements in { 1 1 ¯ 00 } [ 0001 ] slip system. Hereinto, alloying elements occupy preferable Ti sites near slip planes. The elements with a larger radius difference from Ti tend to reduce the GSF energies more dramatically. Moreover, the elements smaller than Ti are more prone to decreasing GSF energies than those larger than Ti. Accordingly, the addition of ternary elements, like Ni, Cu and Co, will lead to an obvious decrease in GSF energies by 18.0%, 16.7% and 13.4% respectively, and therefore may facilitate the initiation of prismatic stacking faults and furthermore enhance ductility. Note that the decline of GSF energies is attributed to the weakening covalent bonds between slip planes with the introduction of ternary elements. Our calculations provide a guide to experiments on the design of Ti 5 Si 3 compounds with tailored properties. [ABSTRACT FROM AUTHOR]

[Display omitted] Monolayer Indium Selenide (ML-InSe) is studied for 4x4 supercell structure through ab initio calculations. The electronic and optical properties of ML-InSe for both pristine and substitutional doped ML-InSe with Palladium (Pd), Platinum (Pt), Silver (Ag), and Gold (Au) atoms have been calculated. With substitutional doping, ML-InSe has been observed to have a spin-dependent electronic structure. The flat energy bands near the Fermi level are observed in ML-InSe with doping elements placed in In site. The flat bands of d orbitals of some noble metal atoms are formed by the projected density of states (PDOS). The PDOS calculations show that the s-orbital of In and p-orbital of Se form the conduction band edge. The energetically favorable position of doping atoms is found to be the Pt In substitution atom according to formation energy calculations. For each studied structure, the bond length of the first neighbor of doping atoms in doped ML-InSe, static dielectric constant (ε 0), refractive index, and energy band gap have been calculated. In the structure ML-InSe with Au Se , ε 0 reaches ∼ 8.15. Another important result is that substitutional doping induces some peaks in the lower energy region of the imaginary part of the dielectric function. These peaks mainly refer to the absorption in related regions and may be important for the optoelectronic properties of ML-InSe. [ABSTRACT FROM AUTHOR]

Spin–orbit coupling (SOC) drives interesting and non-trivial phenomena in solid-state physics, ranging from topological to magnetic to transport properties. A thorough study of such phenomena often requires effective models where the SOC term is explicitly included. However, the estimation of SOC strength for such models mostly depends on the spectroscopy experiments which can only provide a rough estimate. In this work, we provide a simple yet effective computational approach to estimate the onsite SOC strength using a combination of the ab initio and tight-binding calculations. We demonstrate the wider applicability and high sensitivity of our method by estimating SOC strength of materials with varying SOC strengths and the number of SOC active ions. As examples, we consider strongly correlated, topological, and semiconducting materials. We show that the estimated strengths agree well with the proposed values in the literature lending support to our methodology. This simplistic approach can readily be applied to a wide range of materials. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Lattice distortion is a basic characteristic of multi-principal element alloys (MPEAs), or high entropy alloys (HEAs). The severe lattice distortion strategy is an effective way to improve the solid solution strengthening of HEAs, but the phase stability will decrease with the increase in lattice distortion. The trade-off between lattice distortion and phase stability is yet to be investigated. Herein, the complex relationship between lattice distortion and phase stability in the Co-Ni-Cr-Mo-V system has been established by using ab initio calculations, thermodynamic calculations and machine learning methods. The results show that electronegativity difference and valence electron concentration are the most important descriptors in the prediction models of lattice distortion and phase stability, respectively, and the support vector machine algorithm has the highest prediction accuracy in the above two groups of models. The establishment of the relationship between lattice distortion and phase stability in the whole composition space has two meanings. One is to point out that the lattice distortion strategy must consider the temperature factor, and the other is to guide the manufacturing and heat treatment process of HEAs with severe lattice distortion. In addition, the correlations between lattice distortion and constituent elements were discussed. It is pointed out that the V element plays an important role in increasing lattice distortion degree in the Co-Ni-Cr-Mo-V system. This study is helpful to understand the relationship between lattice distortion and phase stability and to promote the development of high entropy alloys with severe lattice distortion. [ABSTRACT FROM AUTHOR]

Understanding high-temperature superconductivity is nowadays a challenge in the area of quantum materials and presents major unsolved problems. The recent discovery of superconductivity in infinite-layer nickelates has provided a new platform for studying unconventional superconductivity. Although the nickelates are analogous to the cuprates high-temperature superconductors, many theoretical analyses indicate that the nickelates do not precisely mirror the cuprates. For instance, hybridization between Ni 3 d x 2 − y 2 and O 2 p is weak, which presents a high contrast to the hybridization between Cu 3 d and O 2 p in the cuprates. The similarities and differences between the nickelates and the cuprates provide great opportunities to reveal the origin of high-temperature superconductivity. In this study, with the employment of first-principles density-functional-theory calculations, we determine and analyze the electronic structure of the undoped infinite-layer nickelate NdNiO 2. By performing phonon calculations and estimating the strength of the electron–phonon coupling, we find that this latter is weak, which indicates that the conventional BCS theory alone cannot explain the observed superconductivity in this material. Consequently, other still-unknown mechanisms may be at play. Moreover, we show from electronic band calculations that another conduction band crosses the Fermi level in addition to the Ni 3 d x 2 − y 2 band. This non-Ni conduction electron band is mainly composed of three orbitals: Nd 5 d 3 z 2 − r 2 , Nd 5 d x y , and another s -like orbital that does not belong to any specific atom. This interstitial s -like orbital is located around the (0,0,0.5) site. The rare-earth orbital Nd 5 d 3 z 2 − r 2 mixes with Ni 3 d x 2 − y 2 at the Fermi level, which causes some holes from the Nd 5 d band to be (self-) doped into the Ni 3 d x 2 − y 2 orbitals. [Display omitted] • DFT electronic structure of NdNiO 2 is calculated. • Electron–phonon coupling in NdNiO 2 is weak. • Ni 3 d x 2 − y 2 , Nd 3 d 3 z 2 − r 2 / 3 d x y contribute to the Fermi surface. • A new s -like orbital centered at (0,0,0.5) also contributes to the Fermi surface. [ABSTRACT FROM AUTHOR]

[Display omitted] The reactions of the γ-U (0 0 1) and (1 1 0) surfaces in contact with O 2 were investigated by density functional theory (DFT), ab initio thermodynamic methods and ab initio molecular dynamics simulations (AIMD). The adsorption of the O atom and O 2 molecule on the (0 0 1) and (1 1 0) surfaces and subsurface are first studied, which provides insights into the adsorption, dissociation, and diffusion of O 2 on the surfaces. Furthermore, the effects of coverages on surface adsorption are considered to help us further understand surface oxidation corrosion. Based on the above research, we can speculate on the initial process of surface corrosion: 1. O 2 molecules in the atmosphere first approach the U surface in the form of physical adsorption; 2. O 2 molecules dissociate into O atoms on the surface; 3. O atoms diffuse on the surface after overcoming a small energy barrier and eventually occupy hollow (H) sites; 4. O atoms penetrate from the H sites to the subsurface; 5. The diffusion of O atoms inside the metal is more likely to be carried out by octahedral interstitial sites. Moreover, the adsorption phase diagrams indicate that O 2 will readily react with U even under ultra-high vacuum conditions, which is consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Based on the results of ab-initio calculations, a new type of 3D carbon-based material, where graphene sheets are connected with each other by carbyne chains, is predicted. A simultaneous presence of three different types of hybridization (sp 1 -sp 2 -sp 3 ) is shown to be the reason for unusual mechanical properties of this material. Four basic types of such 3D-structures are considered, which differ both in the type of contact bonds of the edge atom of the carbyne chain with graphene sheet and in their location on graphene sheet. “Stress-strain” diagrams for these structures are obtained; their strength and elastic properties are ascertained. It is shown that the strength of contact bond in such a structure can reach 67% of maximum attainable strength, which is realized in five-atom carbyne chain. This is one of the main factors, which guarantees extremely high levels of strength of considered 3D-structures. The linear dependence between the strength of contact bond and its equilibrium length is established, which determines the regularities of atomic structure effect on the strength of such structures. It is shown that a combination of high strength with relatively low values of elasticity moduli is a characteristic feature of considered 3D-structures, which is very attractive for both nano-devices and medical applications. [ABSTRACT FROM AUTHOR]

The effects of pressure on the structural, electronic and mechanical properties of tetragonal NbAl 3 and cubic Nb 3 Al have been investigated using first-principles density functional theory approach within the generalized gradient approximation. The calculated structural parameters of two compounds were in good agreement with previous theoretical and experimental data, which linearly decreased with the increasing pressure. The electronic properties of two compounds under pressure have been analyzed. The enhanced covalence under pressure was found due to the increased hybridization between Nb-4d and Al-3p states. The independent elastic constants and mechanical properties have been calculated under pressure. We found that the pressure had a very important influence on mechanical properties. Finally, the ductile/brittle character and mechanical stability of two compounds have been discussed. [ABSTRACT FROM AUTHOR]

We examine the structural and electronic properties of BiNiO 3 and La-substituted BiNiO 3 of triclinic structure (space group P -1) with the use of DFT + U calculations. Both LSDA + U and GGA + U approaches predict the insulating ground state of BiNiO 3 system with G-type antiferromagnetic structure in the range 5 < U < 8 eV. The best agreement with experiment is found for GGA + U with U = 7 eV. Special attention is paid to changes in the calculated Ni O Ni bond angles in BiNiO 3 and La-substituted BiNiO 3 imposed by +U correction. The calculated electron localization function qualitatively reveals the charge disproportionation at Bi sites (Bi 3+ and Bi 5+ ) in the triclinic phase of BiNiO 3 . The total energy calculations of La-substituted BiNiO 3 in the triclinic phase with La replacing Bi 5+ ion show that the G-AFM ordering has the lowest energy for the system containing 25% of La. [ABSTRACT FROM AUTHOR]

A recently synthesized material GdTe 3 has shown very interesting properties like superconductivity and high carrier mobility in its bulk and flake form. Here, we have shown the formation of a monolayer of GdTe 3 from its bulk parent material by means of exfoliation. We have also studied magnetic ground state and electronic properties of bulk and two-dimensional (2D) GdTe 3 , using ab initio calculations. We find both of them to have the same anti-ferromagnetic spin arrangement in their ground state. Our calculations further reveal that both bulk and 2D-GdTe 3 are metallic, mainly because of the electronic contribution arising from the Te-atoms. The magnetic ground state does not change on the inclusion of the Hubbard- U parameter, calculated self-consistently to have a value of 5.7 eV for the Gd- f electrons. The spin–orbit coupling (SOC) calculations in 2D-GdTe 3 , for both U = 0 and 5.7 eV, show that the system prefers an in-plane anti-ferromagnetic ordering and has an easy magnetization axis along the crystallographic a -direction. [Display omitted] [ABSTRACT FROM AUTHOR]

Nanoalloys have been investigated for a wide range of applications, however, our atomistic understanding of the physical-chemistry properties is still far from complete as quantum-size effects play an important role for particles with about 1 nm diameter. In this work, we employed density functional theory calculations to investigate the structural, energetic and electronic properties of 55-atom A 55- n B n nanoalloys, where A , B = Al, Cu, Zn, and Ag. For structure generation, we combined clustering algorithm techniques with design principles, which yields a wide range of conformations. From the analyses of the excess energy results, we found that the CuAl, CuAg, CuZn, and AlAg systems are the most energetically favorable, in particular, the Al 42 Cu 13 and Al 42 Ag 13 compositions (onion-like and core–shell structures, respectively). Through Spearman's correlation analysis, we found that the structural properties (number of under coordinated atoms, effective coordination number, average bond lengths, and chemical order parameter) are the most important descriptors correlated with the energy stability of the nanoalloys (excess energy). Several properties such as the particle volume, binding energy, and average bond length show a linear dependence as a function of composition. [ABSTRACT FROM AUTHOR]

We have performed a multi-methodological theoretical study of impact of thermal vibrations on the Mössbauer effect in the tetragonal β -phase of tin. We have seamlessly combined (i) atomic-scale numerical data in the form of mean square displacements of Sn atoms determined by quantum-mechanical calculations, (ii) continuum-level thermodynamic modeling based on the quasi-harmonic approximation and (iii) theoretical analysis of Mössbauer effect resulting in the prediction of temperature dependence of Mössbauer factor. The computed results were compared with our Mössbauer and X-ray experimental data. We show that classical theoretical approaches based on simplistic Debye model of thermal vibrations of solids can be nowadays replaced by exact ab initio calculations of individual thermal vibrations. While both Debye and our approach slightly deviate from the experimental data, our suggested methodology bears promises for future improvement and a better agreement with measurements, i.e. the prospect that the over-simplified Debye model may not offer. [Display omitted] • We used a multi-methodological approach to temperature trends of Mössbauer effect. • Ab initio calculations of phonons were combined with continuum thermodynamics. • Our approach to Mössbauer factor bears promise for future outperformingDebye model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Calculations of phonon spectrum, mechanical properties, and thermodynamic properties. • α-(Al 0.75 Cr 0.22 Si 0.03) 2 O 3 compound is thermodynamically unstable. • α-(Al 0.75 Cr 0.22 Me 0.03) 2 O 3 exhibits semiconductor characteristics. • Changes in properties are influenced by the differences in electronic structures. α-(Al x Cr 1-x) 2 O 3 thin films have a wide application prospect due to their thermodynamic stable corundum structure and excellent mechanical and thermodynamic properties. In this study, theoretical investigations on the crystal structure, electronic structure, mechanical and thermodynamic properties of quaternary corundum structured α-(Al 0.75 Cr 0.22 Me 0.03) 2 O 3 (Me: Si, Fe, Mn, Ti, V, and Y) compounds have been explored by using ab-initio calculations. Results show that all compounds remain in the corundum structure, with stable mechanical and thermodynamic properties except for α-(Al 0.75 Cr 0.22 Si 0.03) 2 O 3 compound, which exhibits thermodynamic instability. Among all compounds, α-(Al 0.75 Cr 0.22 Fe 0.03) 2 O 3 exhibit the best mechanical properties with the highest modulus and hardness value, H V[TIAN] of 16.65 GPa. Changes in mechanical properties of the compounds result from the varied bonding and antibonding states around the E F. All compounds exhibited excellent semiconductor characteristics with indirect band gaps ranging from 0.03 to 1.51 eV. [ABSTRACT FROM AUTHOR]

• The stability of the M-segregated surface is higher than that of the non-segregated and Cu-segregated surfaces under vacuum condition; • The stability of the non-segregated surface is the highest at the CO coverage of 1/4 ML; • The surface-adsorbate binding strength directly affects the surface segregation tendency in a reactive environment. Segregation on the surface of metal alloys has a great influence on their electrochemical and catalytic properties. We have used ab initio calculations based on density-functional theory to study the surface segregation phenomena of Cu 3 M(1 1 1) (M = Au, Ag, and Zn) alloy systems with chemisorbed CO. The calculated results show that the chemical adsorption of CO can substantially change the segregation tendency of Cu 3 M(1 1 1) surface. The stability of the M-segregated surface is higher than that of the non-segregated and Cu-segregated surfaces under vacuum condition, while the stability of the non-segregated surface is the highest at the CO coverage of 1/4 ML. Moreover, the analysis of the CO adsorption behavior and the surface electronic structure indicates that the surface-adsorbate binding strength directly affects the surface segregation tendency in a reactive environment. This study provides a theoretical basis for the practical application of copper-based alloys as CO 2 reduction catalysts. [ABSTRACT FROM AUTHOR]

Ab intio calculations were done to investigate the structural, elastic, electronic and optical properties of the Cd-containing theoretically predicted MAX phase, Ti 2 CdN, in comparison with the isostructural and already synthesized phase, Ti 2 CdC. These calculations reveal that the substitution of C by N affects the lattice parameter c , whereas the lattice parameter a , remains almost unchanged. All the elastic constants and moduli increase when carbon is replaced by nitrogen. The elastic anisotropy in Ti 2 CdC is higher in comparison with that of Ti 2 CdN. Both these nanolaminates are brittle in nature. The calculated electronic band structures and density of states suggest that the chemical bonding in these two ternary compounds is a combination of covalent, ionic and metallic in nature. Electrical conductivity of Ti 2 CdC is found to be higher than that of Ti 2 CdN. The calculated reflectivity spectra show that both the MAX phases Ti 2 CdC and Ti 2 CdN have the potential to be used as coating materials to minimize solar heating. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) based first-principles investigation has been performed to study the cohesive, elastic and electronic properties of Fe–Zr binary intermetallics across the composition range. Our initial calibration of underlying DFT approximations provides good agreement of lattice parameters and bulk moduli with experimental results. Ground state stability analysis indicates C15-Fe 2 Zr Laves phase to be the most stable and t-FeZr 2 to be more stable than c-FeZr 2 . All Fe–Zr intermetallics are mechanically stable as estimated from their calculated elastic constants. The calculated elastic moduli, in general, decrease with increasing Zr concentration. Anisotropies in bulk, shear and Young moduli are also presented. All the binary intermetallic phases exhibit G/B value of less than 0.57 and hence are ductile due to the presence of dominant metallic bonding arising from Fe d –Zr d interactions with a small component of covalent character. [ABSTRACT FROM AUTHOR]

In this work, the effects of small ternary additions to B2 NiTi structures was investigated through DFT calculations. The analysis considered deviations from stoichiometry arising from either simple substitution of host atoms in a given sublattice or from the formation of anti-sites. The calculations enabled the determination of the site preference of X ternary additions. Moreover, the results suggest that ternary additions located in the central region of the transition metal group across all periods tend to occupy Ni sites due to favorable X–Ti nearest neighbor (NN) interactions. This occupancy is achieved through substitution or through the generation of anti-site defects. On the other hand, ternary additions at both ends of a given transition metal row tend to occupy Ti sites due to favorable X–Ni NN interactions. Once site preferences are determined, the effect of alloying on the thermodynamic and mechanical properties of B2 NiTi–X structures are presented and trends are discussed. [ABSTRACT FROM AUTHOR]

The tendency to dissolve in the matrix for alloying elements such as transition metals and some main group elements in α-Nb 5 Si 3 phase as well as their effects on the structure stability and mechanical properties are important for the performance of niobium-silicide based alloys, which, however, are not clear yet. In this work, we unravel the above problems based on ab - initio calculations. Our results show that the alloyed Nb 5 Si 3 systems become less stable as the alloying elements change from group IVB to VIB in the periodic table. The occupation preferences of the alloying elements depend on their relative atomic radii respect to either Nb or Si. Furthermore, the dissolution of the alloying elements is easier at high temperatures by the Debye model analysis, from which the homogenization-treatment temperatures of alloyed Nb 5 Si 3 phases are also deduced. All alloyed Nb 5 Si 3 phases are mechanically stable, even though their mechanical properties like ductility are not improved. Finally, the electron localized function, Bader charge and densities of states are used to understand the structure stability of alloyed Nb 5 Si 3 , and we find that ionic bonding has quite significant effects on the stability of these intermetallic compounds. [ABSTRACT FROM AUTHOR]

Elastic and thermodynamic properties for the stable phases in the Nb–Al system were studied with the first-principles pseudo-potential plane-wave method based on density functional theory. The temperature dependence of the enthalpy of formation for the NbAl 3 and Nb 2 Al intermetallics are reported for the first time using the quasi-harmonic approximation. The elastic properties of Nb 2 Al and the linear thermal expansion coefficient and the elastic properties versus temperature of the Nb 3 Al are reported for the first time. The calculations would suggest that the NbAl 3 is the stiffest and most brittle of the Nb–Al intermetallics. [ABSTRACT FROM AUTHOR]

Understanding the iron adsorption on the surface of particles is important to predict their nucleation activity and find efficient precipitates. Ab initio calculations of adsorption energy for Fe on the (0 0 1) MX surface ( M = Ti, V, Nb, Zr, Hf or Ta and X = C or N) were performed to study the initialization of Fe nucleation. We find that the trends in Fe adsorption as dependent on the M and X atoms do not follow the lattice parameter or surface energy of MX , but are closely related to the number of the M and X valence electrons. The strongest binding was predicted for Fe on (0 0 1)NbC, and this carbide should have the high nucleation potential at early stage that is consistent with the observed grain refinement of ferritic and austenitic steels with NbC. In order to establish the alloying effect, we studied the adsorption of 3 d atoms ( M = Ti, V, Cr, Mn, Co, and Ni) on (0 0 1)NbC and concluded that Cr and Mn may compete with Fe in adsorption. The calculations of Fe adsorption on the NbC surface covered with 3 d atoms demonstrated that the initial layer of the Cr or Mn atoms enhances the subsequent Fe adsorption. [ABSTRACT FROM AUTHOR]

• The local structure and properties of LaCl 3 melt are studied using machine learning potential. • The machine learning potential enables higher efficiency and similar accuracy relative to DFT. • The machine learning potential can yield precise descriptions of local structure and properties. It has been known for many years that mixtures of lanthanum chloride (LaCl 3) with alkali chlorides in spent nuclear fuel show severe departures from ideality. To go deep into this non-ideality, the local structure of molten LaCl 3 was investigated by experiments and classic molecular dynamics simulations. However, there appears to be some controversy concerning conclusions of these research methodology such as coordination numbers of the first coordination shell. In this work, interatomic potential driven by machine learning is developed based on data sets generated by ab initio calculations in order to research the local structure and property of molten LaCl 3 at 1200 K, 1300 K, 1400 K and 1500 K. The machine learning potential enables higher efficiency and similar accuracy relative to DFT and yields precise descriptions of microstructures and properties. Microstructural evolution with target temperatures is analyzed through partial radial distribution functions, coordination numbers, angular distribution functions and total neutron structural factors. We observe short- and intermediate-range order and the latter disappears at high temperature. The sevenfold and eightfold coordinated structures are dominant in LaCl 3 melt and the network structure is composed of corner-sharing, edge-sharing and face-sharing configurations. Evolution of properties including density and self-diffusion coefficient over the entire operating temperature range are documented. This work exhibits a thorough understanding of the local structure and property of LaCl 3 melt and reveals the accuracy of machine learning potential on molten trivalent metal chlorides for first time. [ABSTRACT FROM AUTHOR]

A robust, modular, and ab initio high-throughput workflow is presented to automatically match and characterize solid–solid interfaces using density functional theory calculations with automatic error corrections. The potential energy surface of the interface is computed in a highly efficient manner, exploiting the high-symmetry points of the two mated surfaces. A database is automatically populated with results to ensure that already available data are not unnecessarily recomputed. Computational parameters and slab thicknesses are converged automatically to minimize computational cost while ensuring accurate results. The surfaces are matched according to user-specified maximal cross-section area and mismatches. Example results are presented as a proof of concept and to show the capabilities of our approach that will serve as the basis for many more interface studies. [Display omitted] • A workflow to compute potential energy surfaces of hetero-interfaces is presented. • Computational parameters and slab thicknesses are converged automatically. • The slabs are matched and strained according to their relative stiffness. • The PESs are sampled by utilizing unique combinations of high-symmetry positions. • Results are collected in an easily shareable and query-able database. [ABSTRACT FROM AUTHOR]

A comprehensive investigation has been made on the ground state, magnetic, ferroelectric and optical properties of the recently synthesized ferroelectric-like LiOsO 3 by first-principle calculations. It is found that the ground state of perfect LiOsO 3 is G type antiferromagnetic (G-AFM) order by both LSDA + U with U eff > 0 eV and HSE. For the G-AFM order, when U eff > 1.75 eV the charge gap opens for LiOsO 3 while the gap is about 0.60 eV by HSE. So the perfect LiOsO 3 should be a G-AFM semiconductor. As for the Li-defected Li 0.94 OsO 3 , the Fermi level shifts to the valence bands. On the other hand the translational periodicity is destroyed by various defects, leading to the disappearance of magnetic order which is responsible for the ferroelectric metal state observed in experiment. This is proved by the decrease of the Os average magnetic moments of Li-defected LiOsO 3 . The calculated spontaneous polarization of perfect LiOsO 3 is about 22.23 μC/cm 2 and the largest component of second order nonlinear optical coefficient is 80.795 pm/V, which indicate that it should be a potential ferroelectric and nonlinear optical material. [ABSTRACT FROM AUTHOR]

The thermal expansion (CTE) of the Cr-based solid-solution compounds in M n +1 AX n phases is explored by ab initio molecular dynamics (AIMD) method. The calculated CTE and thermal expansion anisotropy (TEA) agree well with experimental measurement. The anisotropy is reduced considerably as exemplified in the case of Cr 2 (Al 0.667 Ge 0.333 )C where the CTE of c axis is reduced from 11.2 × 10 −6 /K to 10.3 × 10 −6 /K. For (Cr 1.833 Ti 0.167 )AlC and (Cr 1.333 Ti 0.667 )AlC, the calculated results show that the Ti doping does reduce the average CTE of Cr 2 AlC from 12 to 11. This study demonstrates that a solid-solution approach is a route for tuning a physical property like the thermal expansion. [ABSTRACT FROM AUTHOR]