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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]

Phosphorene's desired bandgap, high carrier mobility and weak spin–orbit coupling qualify it as an exceptional semiconductor spin channel material. These traits underscore the importance of examining phosphorene's electronic structure and that of half-metal heterojunctions (HJs) in innovating spintronic device design. This paper methodically investigates the electronic structure and Schottky barrier (SB) of a van der Waals HJ, comprising phosphorene and the half-metal Co 3 Sn 3 S 2 , subjected to biaxial mechanical strain via a first-principles method. The investigation unveils that phosphorene, as an n-type semiconductor, possesses substantial spin polarization. Remarkably, phosphorene undergoes three states – metallic, half-metallic, and semiconducting – subject to varying strain ratios (E). Furthermore, we discern that phosphorene's spin polarization, peaking at 100% for − 2 % < E < 1 % , is tunable with strain. The SB heights (SBHs) also exhibit a consistent escalation with strain: for − 5 % ≤ E < 1 % , the electron SBH is 0 eV, which increments from 0.017 eV to 0.021 eV for 1 % ≤ E ≤ 3 %. Intriguingly, the spin-down band alignment of the HJ transitions from type-II to type-I at E = 3%. Our Bader charge analysis validates that the n-doping of phosphorene is primarily due to electron acceptance from Co 3 Sn 3 S 2. The orbital hybridizations between phosphorene and Co 3 Sn 3 S 2 leads to complete spin polarization of phosphorene. Collectively, these observations confirm phosphorene's capability to attain n-type doping with 100% spin polarization. Moreover, our findings suggest the possibility to modulate both the bandgap of phosphorene and the SBHs of the HJ with strain. This highlights the potential of the phosphorene/Co 3 Sn 3 S 2 HJ in advancing the field of low-dimensional, flexible spintronics. [Display omitted] • Within the range of − 2 % < E < 1 % , phosphorene achieved 100% spin polarization. This indicates that the electron spins were aligned in a specific direction. • The SB heights of the HJ were found to be strain-dependent. The electron SB height was 0 eV for − 5 % ≤ E < 1 % , and it increased from 0.017 eV to 0.021 eV for 1 % ≤ E ≤ 3 %. • The spin-down band alignment of the HJ was identified as type-II for − 5 % ≤ E < 3 %. However, it changed to type-I at E = 3 %. [ABSTRACT FROM AUTHOR]

The figure of merit of n-type monolayer BiSbS 3 increases with the increase of temperature, and does not show a downward trend in the temperature range studied in this paper. The maximum figure of merit of p-type monolayer BiSbS 3 is 0.78025, which is obtained at a temperature of 1100 K and carrier concentration of 1 × 1020 cm−3. The optimal figure of merit, which is procured from n-type monolayer BiSbS 3 within the range of carrier concentration interval considered in this paper, is about 1.27742 at 1500 K and 5 × 1019 cm−3, which is larger than the maximum figure of merit of p-type monolayer BiSbS 3. The optimal figure of merit of monolayer BiSbS 3 studied in this paper is higher than that of Bi 2 O 2 Se (ZT = 0.53 at 800 K) [87] , Bi 2 O 2 Te (ZT = 0.62 at 800 K) [87] , SnS (ZT = 1.0 at 750 K) and PdTe 2 (ZT = 0.91 at 700 K). [Display omitted] The electronic structure and thermoelectric properties of bulk to monolayer BiSbS 3 are studied by density functional theory and semi-classical Boltzmann transport equation. Meanwhile, it is clear that bulk and monolayer BiSbS 3 are semiconductors with indirect band gaps by using the TB-mBJ scheme, respectively. Further, it can be known that the phonon spectrum of thin film BiSbS 3 has no negative frequency, and it can be inferred further that thin film BiSbS 3 is stable. Monolayer BiSbS 3 studied in this paper has extremely low lattice thermal conductivity at room temperature, which is lower than that of single quintuple layer Bi 2 Te 3 , bulk Sb 2 Te 3 , single-QL Bi 2 Se 3 and Bi 2 Te 3 S at room temperature. The maximum figure of merit of p-type monolayer BiSbS 3 is obtained at a temperature of 1100 K and carrier concentration of 1 × 1020 cm−3. The optimal figure of merit, which is procured from n-type monolayer BiSbS 3 within the range of carrier concentration interval considered in this paper, is obtained at 1500 K and 5 × 1019 cm−3. [ABSTRACT FROM AUTHOR]

Electronic structures that determine the energetics of interatomic bond breaking and reforming are the key parameters to predict and control the mechanical behavior, especially for transition metals/alloys with orientation-dependent bonding characteristics. First-principles calculations are ideal tools to provide accurate information for these electronic features. In this paper, the electronic structure factors that affect the strength and ductility of transition metals and alloys are reviewed from two different aspects. First, the electronic effects on the mechanical properties of perfect crystals, such as elastic modulus and ideal strength behavior, are reviewed. Second, the real deformation behaviors depend on the evolution of deformation defects, such as dislocations and deformation twinning. The recent processes on the studies of electronic structures that affect the stability and mobility of these defects in transition metals and alloys are also summarized. These electronic factors enhance our understanding of fundamental mechanisms of the mechanical properties; they can also be used as key parameters for the design of advanced alloys based computational materials science and machine learning techniques. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Structural, magnetic and optical properties of Mg-doped CeO 2 (1 1 1) surface were investigated. • The doped CeO 2 (1 1 1) surface systems exhibit different bonding character. • The doped surface and subsurface systems result in local and scattered spin atmosphere. • The incorporation of Mg can lead to the red shift of absorption edge. Abstract The electronic structure, magnetic and optical properties of Mg-doped CeO 2 (1 1 1) surface have been investigated by first-principles calculations. In this paper, the doping case is actively favorable to process under O-rich conditions than under Ce-rich conditions. The distortion of doping systems of Mg replacing Ce of surface is larger than that of subsurface. The covalent character is getting weaker and the ionic character is gradually obvious for Mg O bond from surface to subsurface doping. The results show that the existence of defect states with O 2 p orbital character makes spin splitting, causing the local and scattered magnetic moments for surface and subsurface doping of Ce, respectively. And the 9 and 12 atomic layers doping systems exhibit magnetic ground states with different magnetic moments. In particular, the calculated Curie temperature (about 434, 483, 1200 K) is higher than room temperature (RT), therefore, the theoretical results showed that Mg-doped CeO 2 (1 1 1) thin films would can be obtained stable room temperature ferromagnetism (RTFM), which is beneficial to practical application. In addition, the optical properties show that all doped systems are capable of enhancing effective absorption of visible and near-infrared light. [ABSTRACT FROM AUTHOR]

Phenanthrocarbazole (PC)-based organic dye-sensitized solar cells (DSSCs) have been recently reported in experiments with an impressive high power conversion efficiency of over 12%. In this paper we report a computational study of the electronic structures, optical parameters and electron injection properties of a series of five PC dyes and the dye-TiO 2 interfaces. Density functional theory (DFT) and time-dependent DFT (TDDFT) approaches were employed. We show that the incorporation of additional building blocks (indoline, carbazole, triphenylamine, or coumarin) to the PC donor moiety leads to obvious influence on the electronic structures and properties, compared to unitary electron donor PC dye. The binary electron-donor PC based dyes demonstrate better electronic properties and spectroscopic parameters. The calculated injection time of electrons from the excited state of dye to the conduction band of TiO 2 is ideal for DSSC applications. The newly designed coumarin-PC and indoline-PC dyes show desirable energetic, electronic, and spectroscopic parameters for DSSCs. Our results are useful for a better understanding on the design rule of PC based organic dyes for future DSSCs. [ABSTRACT FROM AUTHOR]

In this paper, the composition-dependent electronic-structure and thermodynamic properties for hexagonal wurtzite (WZ) and face-centered cubic zincblende (ZB) ZnS 1− x Se x ternary alloys have been studied utilizing first-principles pseudopotential plane-wave self-consistent field calculations. Special quasi-random structure method was applied to generate disordered structures of 16-atom supercell for x  = 0.25, 0.5 and 0.75. We obtained a direct band-gap at Г point and a shrinking tendency of the band-gap with increasing Se content in both phases. The reasons for the band-gap shrinkage have been discussed based on the analysis of electronic density of states and band offsets. Δ-sol method was applied to correct the band gaps calculated by density functional theory. The Δ-sol corrected band-gaps are in good agreement with experimental band-gaps. The thermodynamic properties were calculated by the cluster expansion method. It turns out that, the stretching forces decrease considerably and linearly with the bond length, while the bending forces are dependent insignificantly on the bond length. The phase diagrams reveal that the lattice vibration effects can influence the critical temperature T c and the solubility of S- and Se-rich ZnS 1− x Se x alloys, but the influence is not obvious for ZB-ZnS 1− x Se x . Based on the calculated phase diagrams without lattice vibration effects, the T c for WZ- and ZB-ZnS 1− x Se x are 559 K and 421 K, respectively. When the vibration enthalpy is included, the T c values of both phases are lowered to 543 K and 418 K, respectively. And if the vibration entropy is also taken into account, the T c values of both phases are further lowered to 529 K and 415 K, respectively. With inclusion of lattice vibration effects, the ZnS 1− x Se x alloy starts a phase transition from ZB to WZ at a temperature of 1600 K, and the solid solubility of Se increases with the temperature rise. [ABSTRACT FROM AUTHOR]

The structural, elastic properties, hardness and electronic structure of Mo 2 FeB 2 alloyed with Cr and Ni have been investigated by using first-principles calculations. The doping concentrations of 2.5 at. %, 5.0 at. %, 10.0 at. % and 20.0 at. % are analyzed systematically in this paper. From the calculated impurity formation energy, it is found that all the structures can retain good structural stability with the doping concentrations of Cr, Ni up to 20.0 at. %. According to the calculated elastic constants, it is observed that Cr can increase the Young’s modulus and hardness and reduce the ductility of Mo 2 FeB 2 markedly with the increasing of alloying concentration. In contrast, Ni can decrease the hardness but improve the ductility of Mo 2 FeB 2 obviously. The calculated electronic structure indicates that the increase of elastic modulus is attributed to the formation of B Cr bond for Cr-doped and B Ni bond for Ni-doped. The Mo Cr and Mo Ni metallic bonds weaken the shear modulus of Mo 2 FeB 2 . When the doping concentration is 20.0 at. %, it is obvious that the alloying elements Cr and Ni can significantly affect the moduli of Mo 2 FeB 2 . [ABSTRACT FROM AUTHOR]

Black phosphorus (BP) is a new two-dimensional (2D) material. It has received significant attention because of its great potential in the field of optoelectronics, which arises due to its low-dimensional effects. In this paper, the effect of bi-axial strain on the band structure of monolayer BP has been studied by using the first-principles method based on density functional theory (DFT). We find that the band gap range of monolayer BP can be moderately and effectively adjusted by external stress from 0 to 1.845 eV. Simultaneously, the direct band gap is maintained during the stretching process, which leads to a high electron mobility suitable for applications. Moreover, the compressive strain can result in a semiconductor–metal transition (SMT) with few-layer BP, whereas tensile strain only affects the band gap. Based on the electronic properties of monolayer BP, its optical properties are analyzed in detail, and the influence of strain—from a compressive strain of 12% to a tensile strain of 12%—on these properties is systematically discussed. It is found that the strain range and mode have a significant impact on the optical properties. In addition, the dielectric function and absorption spectra calculated along two different directions indicate that a significant optical anisotropy appears, giving a strong directionality dependence in the primitive and strained monolayer BP. It can be concluded that by applying external stress to monolayer BP, its optical properties can be readily controlled, which is beneficial for device applications. Furthermore, based on its direction-dependent response to the external stress, this behavior can also be used to detect the orientation of the deposited BP without the need for precise electron microscopy. [ABSTRACT FROM AUTHOR]

In the paper, the electronic properties and magnetic orderings in the Mn/Gd doped zinc-blende (ZB) and wurtzite (WZ) structural CdSe are investigated extensively using first-principles calculations. We find that the infiltration of Mn ions in the ZB/WZ structural CdSe will lead to the antiferromagnetic ordering; while the infiltration of Gd ions will lead to the ferromagnetic ordering. Moreover, the antiferromagnetic/ferromagnetic coupling interactions between the magnetic Mn/Gd ions will become more and more strong with decreasing Mn-Mn/Gd-Gd distance. Particularly, the electronic properties in the Mn mono-doping case (spin-polarized) and in the Mn double-doping case (ferromagnetic) are almost same, and they tend to be the magnetic/ferromagnetic semiconductor via the comparison from the different calculations; as a whole, the Mn doped ZB/WZ structural CdSe system tends to present the antiferromagnetic semiconductor character. In addition, the band gap in the Mn doped ZB/WZ structural CdSe decreases with increasing Mn concentration using GGA+U calculations. In contrast to the case of the Mn doped ZB/WZ CdSe: (i) the Gd doped ZB/WZ CdSe in the mono-doping case displays the magnetic semiconductor character; but the Gd doped ZB/WZ structural CdSe in the double-doping case presents the n-type ferromagnetic semiconductor, and the robust ferromagnetism is obtained in the system irregardless of the crystal structure and the distance between the magnetic ions; (ii) the band gap in the Gd doped ZB/WZ structural CdSe increases with increasing Gd concentration, Burstein-Mott-effect might be major reason. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO 2 ) is an attractive transition metal oxide owing to its intriguing metal to insulator phase transition and has great potential for applications in smart windows. In this paper, first-principles calculations were conducted and the results revealed that Sb is as an efficient dopant in improving the thermochromic properties of VO 2 by lowering the phase transition temperature and enhancing the transmission of visible light, as well as increasing the near-IR absorption of VO 2 . These changes in the optical properties of VO 2 are closely correlated with the variations in the atomic and electronic structures, where the V V chains along the [0 0 1] direction present dimerization features in VO 2 (R) with Sb-doping; in addition, the O V bonds appear less ionic due to the O Sb ionic bonds. The calculation results are confirmed by the subsequent experiments, suggesting that our findings would be useful for further understanding the physics of atomic doping in VO 2 , which may provide useful guidance for the fabrication of high-quality VO 2 based smart windows. [ABSTRACT FROM AUTHOR]

[Display omitted] It is an important research goal to find new environment-friendly and stable materials for sustainable and green energy applications. This paper reports a new type of super alkali perovskite Li 4 NBI 3 (B = Ge, Sn, or Pb) with high mobility that was designed and studied by using the first-principle calculation method based on density functional theory. The geometrical structures, thermodynamic stability, electronic properties, transport properties, mechanical properties, and optical absorption properties of Li 4 NBI 3 perovskites were calculated. The effects of the super alkali cluster Li 4 N on the structure and electronic properties of these perovskites were investigated. The results show that ionic bonds are formed between Li 4 N and I, and that the local energy state provided by Li 4 N increases the density of states at the edge of the energy band, which affects the energy band structure and pseudo-bandgap, and further affects the optical absorption coefficient and carrier mobility. Mechanical parameters showed that these three perovskites have high ductility, so they are suitable for making thin films. With high conductivity, strong light absorption, these perovskites are likely to become potential candidates for new energy materials. [ABSTRACT FROM AUTHOR]

The single-layer MoS 2 has drawn extensive attention due to its appealing properties for device applications. In this paper, a new porous MoS 2 (so-called as P-MoS 2 ) is theoretically explored. Compared with conventional H-MoS 2 , P-MoS 2 has quite different crystal structure, and more importantly, it possess 27% larger specific surface area, making it superior candidates in energy industry and catalysts. Furthermore, P-MoS 2 becomes metallic from semiconducting H-MoS 2 . Finally, P-MoS 2 transforms back to a semiconductor with tunable band gap by changing applied strains. Our studies enrich the family of MoS 2 nanostructures, and also extend the application range. More interestingly, it also provides a platform of exploring other porous TMDs with diverse electronic structures. [ABSTRACT FROM AUTHOR]

Obtaining a bright and low emittance electron beam directly from the photocathode is mandatory in order to design high performance free electron lasers (FELs). To achieve this goal a clear understanding of how the emission process is influenced by structure, morphology and composition of the photocathode surface is needed. This is difficult from an experimental point of view because often the atomic scale details of the surface whose emission has been measured are unknown. A predictive theoretical approach capable of determining the effects of surface structure on emission is therefore or great interest. A model to extend the well known three step model (as proposed by Berglund and Spicer) to surface calculations is discussed in this paper. It is based on a layer-by-layer decomposition of the surface electronic structure that can be calculated through reliable and efficient DFT calculations. The advantage of this approach with respect to other existing photoemission calculations is being able to correlate directly the photoemission to the electronic, atomic and chemical structure of the surface. The proposed approach retains, therefore, the simple chemical intuition in the study of surface modifications and their effect on the photoemission. The approach is validated in calculations of the emission from clean copper and silver surfaces. The ability of the model to simulate the change in photoemission in response to adsorbates is tested by simulating monolayers of oxygen, hydrogen and lithium on the copper (1 1 1) surface. [ABSTRACT FROM AUTHOR]

In recent years, the Berry phase as a fascinating concept has made a great success for interpreting many physical phenomena. In this paper, we review our past works on the Berry phase effect in solid materials with spin–orbit coupling. Firstly, we developed an exact method for directly evaluating the Berry curvature and anomalous Hall conductivity, then the intrinsic mechanism of anomalous Hall effect was quantitatively confirmed in bcc Fe and CuCr 2 Se 4− x Br x . An effective method was proposed to decompose the anomalous Hall effect into the intrinsic and extrinsic contributions. We also developed computational methods for the spin Hall conductivity and anomalous Nernst conductivity. Secondly, we developed a powerful method for computing the Z 2 topological invariant without consideration of special symmetry. We predicted many topological insulators in three-dimensions, including half-Heusler, chalcopyrite, strained InSb, core-holed Ge and InSb, Bi 2 Te 3 /BiTeI heterostructure, and in two-dimensions, including silicene, germanene, stanene, X-hydride/halide (X = N–Bi) monolayers and Bi 4 Br 4 . We also predicted the quantum anomalous Hall effect in magnetic atoms adsorbed graphene and half-passivated BiH, the quantum valley Hall effect and topological superconducting in silicene and n -dopped BiH. Finally, the summary of our past works and the further outlooks are discussed. [ABSTRACT FROM AUTHOR]

In this paper we have investigated the physical and transport properties of Bismuth Selenide, (Bi 2 Se 3) intercalated with Silver (Ag) (Gold (Au) is included for comparison) via dynamical mean field theory with local density approximation. The band structure of Bi 2 Se 3 with a Dirac cone is strongly influenced by the intercalation phenomena at moderate densities which eventually leads to an orbital selective metal insulator transition leading to superconductivity at low temperatures. The claims on the orbital selectivity are substantiated by computing the density of states. While the onset of superconducting correlations at low temperatures are supported by a sudden drop in the resistivity as a function of temperature and the nature of susceptibility. Further the Fermi surface (FS) maps for low and high temperature yields no FS reconstruction. [ABSTRACT FROM AUTHOR]

The structural, elastic and electronic properties of four nitrides M 2 N 3 (M = Zr, Hf, W and Re) with U 2 S 3 structure are investigated by plane-wave pseudopotential density functional theory by the generalized gradient approximation in this paper. The calculated elastic constants show that the nitrides are mechanically stable at ambient conditions, except Re 2 N 3 . The calculated bulk modulus B and shear modulus G indicate that Zr 2 N 3 , Hf 2 N 3 and W 2 N 3 are potential candidates for hard materials. [ABSTRACT FROM AUTHOR]

MoS2-WS2 thin layers with different deposition sequences and stacking configurations have been studied using first principles full potential linearized augmented plane wave method. The electronic and optical properties of ten atomic layers (in [0 0 0 1] direction) of MoS2-WS2 are reported in the present paper. Ten layers of MoS2-WS2, which are free from quantum size effects, show an indirect band gap which varies between 0.89 and 1.22 eV by engineering of the layering sequence and stacking configuration. Optical properties like absorption coefficients, dielectric tensors and refractive indices of bilayer and multilayer films of MoS2-WS2 are determined and are found to be different from the ten layers of MoS2 and WS2. Changes in the electronic and optical properties of multilayers have been elaborated in terms of interlayer and intralayer S-S distances. A comparison of absorption spectra deduced using the first principles calculations for Si and different combinations of multilayers of MoS2-WS2 show their applicability in optoelectronics and photovoltaic devices. [ABSTRACT FROM AUTHOR]

In this paper, first-principles calculations based on density functional theory are used here to investigate the electronic structures and lattice dynamics of ternary intermetallic compounds MAlSi (M = Ca, Sr, Ba) under high pressures. Electronic topological transitions (ETTs) occur at high pressures in CaAlSi and SrAlSi, but not in BaAlSi. A study of the lattice dynamics of CaAlSi and SrAlSi under pressures reveals that the low-lying optical phonon mode softens at H point, but the acoustic phonons harden with the increase of pressure. It is indicated that the ambient-pressure structures of these intermetallic compounds are unstable under high pressure, and new structures should be stabilized. [ABSTRACT FROM AUTHOR]

Highlights: [•] Elastic, electronic, magnetic and thermodynamic properties of Ni2ZrX (X=Sn, Sb) are investigated. [•] The first-principle calculations and quasi-harmonic Debye model are used in this paper. [•] Optimized lattice constants, Bulk and Shear moduli, ductility and Poisson’s ratio are obtained. [•] The effect of T and P on Cv is opposite and the effect of T and P on α is small. [•] Ni2ZrX alloy has little magnetism due to different atomic position in the generalized Heusler alloy. [ABSTRACT FROM AUTHOR]

[Display omitted] Intrinsic defects and hydrogen play an essential role in regulating photocatalytic properties of semiconductor materials. Bismuth oxychloride (BiOCl) is an important ternary bismuth-based photocatalytic material, for its wide bandgap allows band-gap engineering to tailor its properties. In this paper, we use first-principles to study the effects of intrinsic defects and hydrogen on the electronic structure of BiOCl. We studied the intrinsic defect formation energies, defect electronic structures and the diffusion of these defects in BiOCl. We found that the p -type conductivity and band gap variation in BiOCl may be caused by the Fermi level pinning effect and intrinsic defective states around the band edges. Intrinsic defects of H int , O Cl and Bi Cl show delocalized features which may have a predominant effect for carrier transfer. As the temperature rises, the diffusion of oxygen vacancies in the xy plane goes up most drastically, while the diffusion of interstitial hydrogen in the yz plane changes smoothest and has the fastest speed. Our work offers fundamental insights for explaining the band gap variation, p -type conductivity and the transport of defects in BiOCl and provides basic guidance in regulating the photocatalytic performance of BiOX (X = Cl; Br; I) by defect engineering. [ABSTRACT FROM AUTHOR]

Recent research in materials science opens exciting perspectives to design novel quantum materials and devices, but it calls for quantitative predictions of properties which are not accessible in standard first principles packages. PAOFLOW , is a software tool that constructs tight-binding Hamiltonians from self-consistent electronic wavefunctions by projecting onto a set of atomic orbitals. The electronic structure provides numerous materials properties that otherwise would have to be calculated via phenomenological models. In this paper, we describe recent re-design of the code as well as the new features and improvements in performance. In particular, we have implemented symmetry operations for unfolding equivalent k -points, which drastically reduces the runtime requirements of first principles calculations, and we have provided internal routines of projections onto atomic orbitals enabling generation of real space atomic orbitals. Moreover, we have included models for non-constant relaxation time in electronic transport calculations, doubling the real space dimensions of the Hamiltonian as well as the construction of Hamiltonians directly from analytical models. Importantly, PAOFLOW has been now converted into a Python package, and is streamlined for use directly within other Python codes. The new object oriented design treats PAOFLOW 's computational routines as class methods, providing an API for explicit control of each calculation. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we have investigated the electronic, optical and mechanical properties of the Y2O3 crystal by first-principle calculations based on the density–functional theory. The generalized gradient approximation (GGA-PBE) and hybrid exchange–correlation functional (HSE06) are both used for comparative study. It is found that, the band gap of Y2O3 calculated by HSE06 method (6.0eV) is in good agreement with the experimental band gap data (5.5eV), and HSE06 gives better electronic structure description close to experiments. Then we calculate the elastic constants, and derive the corresponding properties i.e.; bulk, shear and Young’s moduli, and Poisson’s ratio. Our calculated elastic and mechanical properties correspond well with experimental data. Besides, we also obtain the equilibrium lattice and bulk modulus of yttria by fitting the Birch–Murnaghan equation of state. It is found that, the HSE06 well reproduce the experimental lattice parameters, equilibrium volume and bulk modulus of Y2O3. Based on the accurate described crystal and electronic structure and mechanical properties by HSE06 method, the optical properties of this material are also analyzed. [Copyright &y& Elsevier]

Abstract: The structural, magnetic and electronic properties of Te-doped BiF3 were investigated by first-principles calculations in this paper. We focused on Te x Bi1− x F3 systems, in which x is equal to 0, 3.125atom%, 6.25atom%, 12.5atom% and 25atom% of Te doping concentration, respectively. The formation energy analysis indicates that the difficulty of Te doping BiF3 decreases with the increase of Te doping concentration, and Te doping BiF3 is much easier in the F-rich conditions than in the Bi-rich conditions. Besides, the calculated cohesive energy of Te doping BiF3 shows that the stability of Te doped BiF3 becomes worse with the increase of Te doping concentration. What is more, Te doped BiF3 shows obvious magnetic character. As for electronic properties of Te-doped BiF3, the results show that the band gap of Te x Bi1− x F3 decreases with the increase of Te doping concentration. For TeBi3F12, TeBi7F24 and TeBi15F48, Fermi level shifts into the spin-up conductivity band while spin-down energy band has a band gap at Fermi level, and thus the compounds exhibit half metallic characters with good conductivity when Te atoms substitute partly Bi atoms. [Copyright &y& Elsevier]

Abstract: Information on the CaAl2Zn2 compound is important for the development of Ca added Mg–Al–Zn alloys. In this paper, the dependences of the structural, electronic, elastic and thermodynamic properties of CaAl2Zn2 compound on pressure were investigated for the first time by means of the first-principles method based on the density functional theory with generalized gradient approximation and local density approximation. It was found that the pressure has significant effects on the equilibrium volume, elastic properties and electronic properties. Our calculated structural data are in good agreement with the previous experimental data results at zero pressure. The calculated anisotropy factors AG and AE and linear compressibility coefficients kc /ka are used to estimate anisotropic elasticity. The isotropic bulk modulus B, shear modulus G, Young’s modulus E, and Poisson’s ratio ν of polycrystalline CaAl2Zn2 compound were determined using the Voigt–Reuss–Hill averaging scheme. The B/G and microhardness parameter H are also calculated. The band structure and density of states are discussed from theoretical viewpoint. The Debye temperature can be obtained from the knowledge of the elastic constants and the sound velocities. The calculated elastic constants indicated that this compound is ductile at different pressures. [Copyright &y& Elsevier]

Abstract: Recent advances in computational materials science present novel opportunities for structure discovery and optimization, including uncovering of unsuspected compounds and metastable structures, electronic structure, surface, and nano-particle properties. The practical realization of these opportunities requires systematic generation and classification of the relevant computational data by high-throughput methods. In this paper we present Aflow (Automatic Flow), a software framework for high-throughput calculation of crystal structure properties of alloys, intermetallics and inorganic compounds. The Aflow software is available for the scientific community on the website of the materials research consortium, aflowlib.org. Its geometric and electronic structure analysis and manipulation tools are additionally available for online operation at the same website. The combination of automatic methods and user online interfaces provide a powerful tool for efficient quantum computational materials discovery and characterization. [Copyright &y& Elsevier]

Abstract: Empirical databases of crystal structures and thermodynamic properties are fundamental tools for materials research. Recent rapid proliferation of computational data on materials properties presents the possibility to complement and extend the databases where the experimental data is lacking or difficult to obtain. Enhanced repositories that integrate both computational and empirical approaches open novel opportunities for structure discovery and optimization, including uncovering of unsuspected compounds, metastable structures and correlations between various characteristics. The practical realization of these opportunities depends on a systematic compilation and classification of the generated data in addition to an accessible interface for the materials science community. In this paper we present an extensive repository, aflowlib.org, comprising phase-diagrams, electronic structure and magnetic properties, generated by the high-throughput framework AFLOW. This continuously updated compilation currently contains over 150,000 thermodynamic entries for alloys, covering the entire composition range of more than 650 binary systems, 13,000 electronic structure analyses of inorganic compounds, and 50,000 entries for novel potential magnetic and spintronics systems. The repository is available for the scientific community on the website of the materials research consortium, aflowlib.org. [Copyright &y& Elsevier]

Abstract: The low-index surfaces of WC polymorphs are calculated using the first-principles method based on density functional theory. It is found that there are large relaxations within the top three layers for all termination surfaces, and charge density falls greatly toward the vacuum. The outermost and second interlayer relaxations for C-terminated surfaces are much larger than those for W-terminated surfaces. The surface energies for all low-index surfaces are large which is due to the breaking of strong W–C bonds. For both WC polymorphs, the C-termination surfaces are thermodynamically more unstable than W-terminated surfaces over the whole range of carbon chemical potentials considered in this paper; the most stable surfaces correspond to the (001) surface with W termination for α-WC, and the (001) surface with WC termination for β-WC. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents Density-Functional Perturbation Theory (DFPT) calculations on the electronic, vibrational, and electron–phonon (EP) coupling properties of the Mg2Si thermoelectric compound. The DFPT yields very satisfactory results for the electronic and vibrational properties when compared to experiment. Regarding the EP interactions, as far as we know, they have never been reported so far. We show that the EP interactions in Mg2Si mainly involve the silicon atom. This result explains the improvement of the thermoelectric properties of Mg2Si using a solid solution Mg2Si1−x A x , where A is a heavier atom than Si. By guiding the choice of the substitution site, the study of the EP coupling properties could be used in the search of new thermoelectric materials based on solid solutions. [ABSTRACT FROM AUTHOR]

Abstract: We present a systematic theoretical study for the structural, elastic and electronic properties of TaB2 with AlB2 structure under pressures ranging from 0GPa to 120GPa within the framework of density-functional theory in this paper. The results at zero pressure are in good agreement with available theoretical and experimental values. Our attention has been focused on high pressure behavior of TaB2. The pressure dependence of structure, elastic constants, Debye temperature, and density of states (DOS) are successfully calculated and discussed. [ABSTRACT FROM AUTHOR]

Abstract: HfTaO3N is an important material in the future industrial applications. However, there are no data in the literature about these analysis. In this paper, structural parameters, elastic, electronic and bonding properties of HfTaO3N have been investigated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory (DFT). These properties of HfTaO3N have been firstly theoretically predicted, which await experimental confirmation. [ABSTRACT FROM AUTHOR]

Abstract: The present paper reports a comprehensive first-principles calculation of lattice dynamical properties of lanthanum nitride, using the relativistic separable dual-space Gaussian pseudopotentials and local density approximation. Our results concerning equilibrium lattice parameter and bulk modulus agree well with the available experimental and previous theoretical data. The phonon dispersion curves and related properties in both ambient rocksalt (RS) and high pressure cesium chloride (CsCl) structures are reported for the first time which shows rocksalt as more stable structure similar to other calculations. The electronic and mechanical properties are also discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the first-principles pseudopotential total energy method is used to predict the structural, electronic and elastic properties of the M3AlC2 (MAX) phases, where M=3d, 4d, and 5d early transition metals. Specifically, the effects of the valence electron concentrations (VEC) of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W were examined. The lattice constants are a linear function of the atomic diameter of the M element. In general, M d–Al p hybridizations locate just below the Fermi level and are weaker than the M d–C p bonds, which are deeper in energy. The bulk moduli of the ternary carbides are found to be proportional to the bulk moduli of the corresponding binary carbides. Because the M–Al bonds are less stiff than the M–C bonds, the latter are mainly responsible for the high bulk moduli of the M3AlC2 phases. The M–Al bonds, on the other hand, play a critical role in decreasing the bulk moduli compared to the binary carbides. [Copyright &y& Elsevier]

Abstract: This research aims at replacing the conventional filament type resistor piezoresistive sensor with a square conductor with four electrical contacts. The four-contact conductor, popularly known as van der Pauw (VDP) structure, is a test structure widely used for measuring resistivity of arbitrarily shaped samples of constant thickness. Over the years, many researchers have extended the original ideas to develop a variety of approaches for evaluating the resistivities of both isotropic and anisotropic materials using VDP type structures. When used as pressure sensors, VDP devices have the potential to obviate some of the limitations of resistor based sensors. In this paper, finite difference and Finite Element Analysis (FEA) methods have been used to model a square VDP structure under biaxial stress condition. The FEA method was also used to model a serpentine filament resistor. It is observed that the sensitivity of VDP based sensor is more than three times higher than the conventional filament type sensor. In addition, this sensor is seen to have no drift while measuring normalized resistance change difference (NRCD). The sensor is also size independent. Thus, the sensor can be made very small without losing its sensitivity with no drifting issues. As the future applications of MEMS focus on integrating various sensing devices in a small area to reduce weight and cost, an alternative small-size piezotransducer will be beneficial for such future applications. [Copyright &y& Elsevier]

Abstract: We studied the structural, electronic and elastic properties of åkermanite, Ca2MgSi2O7, by using the first-principles method. The structure of åkermanite is constructed by interleaved tetrahedral and Ca cation layers, and this characteristic is perfectly presented by three-dimensional (3D) crystal lattice, as well as two-dimensional (2D) contour plots of total electron densities in this paper. The chemical bonding and interaction are investigated by analyzing the bond population and density of states (DOS) of the crystal. Theoretical elastic constants of åkermanite are consistent with the experimental values. Moreover, significant anisotropy for Young’s modulus can be observed. [Copyright &y& Elsevier]

Abstract: In this paper, we study the structural, elastic and electronic properties of perovskite LaAlO3 using two different methods: the full-potential linearized augmented plane wave (FP-LAPW) method and the pseudopotential plane wave (PP-PW) scheme in the frame of generalized gradient approximation (GGA). We have evaluated the ground-state quantities such as lattice parameter, bulk modulus and its pressure derivative as well as the elastic constants. Also, we have presented the results of the band structure, densities of states and charge densities. These results were in favourable agreement with previous theoretical works and the existing experimental data. To complete the fundamental characteristics of this compound we have analyzed the thermodynamic properties using the quasi-harmonic Debye model. [Copyright &y& Elsevier]

Abstract: In this paper, we report theoretical calculations based on ab initio total energy calculations using the full potential linearized augmented plane wave (FP-LAPW) method and the plane wave method with ultrasoft pseudo-potential (UPP) scheme in the frame of generalized gradient approximation (GGA). These calculations are the first step in the investigation of structural, electronic properties of Damiaoite PtIn2. The thermodynamic properties will be calculated using the quasi-harmonic Debye model, in which the isothermal bulk modulus, thermal expansion coefficient, and specific heat for high pressures and temperatures are investigated. The major electronic trends show that PtIn2 in Damiaoite structure is metallic with covalent bonding nature. The elastic properties calculations show that our system is mechanically stable but lower hard. [Copyright &y& Elsevier]

Abstract: The short-period group-III nitrides superlattices (SL’s) are now receiving a particular intention. Depending on the technique and conditions of growth, a number of many types of chemical ordering in nitride alloys can take place. It is demonstrated that partial ordering in these new structures reduces the band gap. In this paper, we investigate the electronic structure of short-period m × n AlN/GaN superlattices (with m, n ⩽3) calculated in wurtzite (with (0001) orientation) structure using a first-principles full potential linearized augmented plane waves method within the local density approximation (LDA). The calculated gaps range from 3.1 for Al-rich to 2.6 (eV) for Ga-rich m × n (001) AlN/GaN systems. We point out that ordering affects significantly the 1×1 (001) InN/GaN and InN/AlN electronic band structures compared to 1×1 (001) AlN/GaN. The 1×1 (001) InN/GaN and InN/AlN are found to have direct smaller band gaps of 0.4 and 1.1 (eV), respectively. The origin of the reduction in the band gaps in InN/GaN and InN/AlN is discussed, as well as the effects of increasing the monolayer number in AlN/GaN superlattices. [Copyright &y& Elsevier]

Semiconductor nanostructures show many special physical properties associated with quantum confinement effects, and have many applications in the opto-electronic and microelectronic fields. However, it is difficult to calculate their electronic states by the ordinary plane wave or linear combination of atomic orbital methods. In this paper, we review some of our works in this field, including semiconductor clusters, self-assembled quantum dots, and diluted magnetic semiconductor quantum dots. In semiconductor clusters we introduce energy bands and effective-mass Hamiltonian of wurtzite structure semiconductors, electronic structures and optical properties of spherical clusters, ellipsoidal clusters, and nanowires. In self-assembled quantum dots we introduce electronic structures and transport properties of quantum rings and quantum dots, and resonant tunneling of 3-dimensional quantum dots. In diluted magnetic semiconductor quantum dots we introduce magnetic-optical properties, and magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot. [Copyright &y& Elsevier]

This paper focuses on describing the computational chemistry software, NWChem, and its use in materials science research. The current functionalities and capabilities are outlined, as well as future features. Specific computational examples are given to show the flexibility and usefulness of NWChem to answering materials science problems. [Copyright &y& Elsevier]

In this paper we address the issue of C and Si vacancy diffusion in SiC by means of first principles electronic structure calculations. Besides a thorough analysis of the stable configurations involved, we characterize the minimum energy paths and the corresponding barriers of all the relevant diffusion mechanisms. [Copyright &y& Elsevier]

Aluminene, one of the group III elemental monolayers, is predicted to be stable in the honeycomb configuration with metallic characteristics. In this paper, we consider aluminene-based heterostructures, investigating their stability, structural and electronic properties. The results based on density functional theory find that the interaction between aluminene and BN or graphene monolayers is weak, and is dominated by the van der Waals forces. The electronic structures calculated using the HSE06 functional show aluminene/graphene and aluminene/BN bilayers to be metallic. Likewise, graphene/aluminene/graphene trilayers are predicted to be metallic. However, BN/aluminene/BN trilayers are predicted to be semiconducting in nature with finite gaps. The results suggest that the interaction of Al atoms with N atoms facilitates the opening up of the gap in trilayer heterostructures, unlike the graphene/BN heterostructures, where inequivalence of the carbon lattice leads to the bandgap. The stacking-dependence of the electronic structure is affirmed by the electron tunneling characteristics calculated for the trilayer heterostructures. The predicted relationship between topology and electronic structure can, therefore, be exploited to tailor the electronic properties of aluminene-based heterostructures. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenide materials are of great interest for the development of semiconductor devices because of their diverse properties. In this paper, we discovered the ground states of W x Mo 1− x S 2 alloys and discussed their electronic structures and phonon properties in detail by the cluster expansion method and the first principle calculation. Three ground-state structures of W x Mo 1− x S 2 alloys, W 1/3 Mo 2/3 S 2 , W 1/2 Mo 1/2 S 2 , and W 2/3 Mo 1/3 S 2 , have low order–disorder phase transition temperatures, T 1/3 = 102.3 K, T 1/2 = 87.8 K, and T 2/3 = 102.2 K, estimated by mean field theory. Their bandgaps exhibit a nonlinear increase with increasing W content. All ground structures are dynamically stable without imagine frequency in phonon dispersion. W doping into single layer MoS 2 leads low frequency optical modes hybriding with acoustic modes and lowering down the low frequency band due to larger mass of W atoms. All these may improve the developments of W x Mo 1− x S 2 alloys devices. [ABSTRACT FROM AUTHOR]

The phase transition between lambda-Ti 3 O 5 and beta-Ti 3 O 5 can be driven by light irradiation, pressure, heat or electrical current, so it has broad application prospects in many fields. In this paper, the electronic and atomic structures of lambda-Ti 3 O 5 and beta-Ti 3 O 5 are calculated using first principle method, and the metal-insulator phase transition between lambda-Ti 3 O 5 and beta-Ti 3 O 5 is investigated. The study found that beta-Ti 3 O 5 is Mott-Hubbard insulator. Through the analysis of the arrangement of atoms of lambda-Ti 3 O 5 and beta-Ti 3 O 5 crystal structures, we found that the metal-insulator transition between lambda-Ti 3 O 5 and beta-Ti 3 O 5 conforms to the bandwidth-controlled transition. [ABSTRACT FROM AUTHOR]

Abstract: The Cu–O based spin chain system A2CuO3 (A=Sr, Ca) has attracted considerable attention of scientists during the last decades due to its unique electronic structure. This paper presents a ground state optimization for the periodic structure of Ca2CuO3 using the Density Functional Theory (DFT). The electronic structure analysis was carried out on the basis of cell optimization using the PBE functional with DNP basis set. Until now, the numerical results were obtained only with exclusion of CaO bilayers from full ab initio treatment. We demonstrate here that the correct covalent insulating ground state may be obtained if the antiferromagnetic interaction along the spin chain is included. The best estimated band gap is 0.79eV. We also show that the CaO bilayers sufficiently contributed to the distribution of d-states above Fermi level. [ABSTRACT FROM AUTHOR]