Search

Borosilicate glasses form an important glass forming system in both glass science and technologies. The structure and property changes of borosilicate glasses as a function of thermal history in terms of cooling rate during glass formation and simulation system sizes used in classical molecular dynamics (MD) simulation were investigated with recently developed composition dependent partial charge potentials. Short and medium range structural features such as boron coordination, Si and B Qn distributions, and ring size distributions were analyzed to elucidate the effects of cooling rate and simulation system size on these structure features and selected glass properties such as glass transition temperature, vibration density of states, and mechanical properties. Neutron structure factors, neutron broadened pair distribution functions, and vibrational density of states were calculated and compared with results from experiments as well as ab initio calculations to validate the structure models. The results clearly indicate that both cooling rate and system size play an important role on the structures of these glasses, mainly by affecting the ³B and 4B distributions and consequently properties of the glasses. It was also found that different structure features and properties converge at different sizes or cooling rates; thus convergence tests are needed in simulations of the borosilicate glasses depending on the targeted properties. The results also shed light on the complex thermal history dependence on structure and properties in borosilicate glasses and the protocols inMDsimulations of these and other glass materials. [ABSTRACT FROM AUTHOR]

We develop a multi-step workflow for the discovery of conventional superconductors, starting with a Bardeen–Cooper–Schrieffer inspired pre-screening of 1736 materials with high Debye temperature and electronic density of states. Next, we perform electron-phonon coupling calculations for 1058 of them to establish a large and systematic database of BCS superconducting properties. Using the McMillan-Allen-Dynes formula, we identify 105 dynamically stable materials with transition temperatures, TC ≥ 5 K. Additionally, we analyze trends in our dataset and individual materials including MoN, VC, VTe, KB6, Ru3NbC, V3Pt, ScN, LaN2, RuO2, and TaC. We demonstrate that deep-learning(DL) models can predict superconductor properties faster than direct first-principles computations. Notably, we find that by predicting the Eliashberg function as an intermediate quantity, we can improve model performance versus a direct DL prediction of TC. We apply the trained models on the crystallographic open database and pre-screen candidates for further DFT calculations. [ABSTRACT FROM AUTHOR]

Polyphthalocyanines (PPCs) are a new and promising class of two dimensional materials offering versatile avenues for next generation electronic devices. For organic spintronic devices, PPCs can be engineered to tailor the electric and magnetic properties. In this work, we investigate PPC's monolayers with embedded transition metal atoms (TM = Fe, Ni, Cu), utilizing first principle calculations based on spin-polarized generalized gradient approximation (SGGA). PPC sheets with central TM atoms are simulated for the dispersion curves, electronic density of states (DOS), and projected density of states (PDOS) using quantum atomistic toolkit (Quantum ATK) software. According to simulations, the FePPC supercell with four magnetic moments of Fe, aligned in a parallel ferromagnetic (FM) configuration, show the conductive FM state, while in the case of the anti-parallel antiferromagnetic (AFM) order of the magnetic moments, the material exhibits semiconducting non-magnetic behavior. FM-ordered NiPPC displays a metallic state, which is partly suppressed for AFM-ordered NiPPC. In contrast, non-magnetic CuPPC is found to be the best conductor due to its larger PDOS at the Fermi level among all considered systems. [ABSTRACT FROM AUTHOR]

Interplay of magnetism and electronic band topology in unconventional magnets enables the creation and fine control of novel electronic phenomena. In this work, we use scanning tunneling microscopy and spectroscopy to study thin films of a prototypical kagome magnet Fe3Sn2. Our experiments reveal an unusually large number of densely-spaced spectroscopic features straddling the Fermi level. These are consistent with signatures of low-energy Weyl fermions and associated topological Fermi arc surface states predicted by theory. By measuring their response as a function of magnetic field, we discover a pronounced evolution in energy tied to the magnetization direction. Electron scattering and interference imaging further demonstrates the tunable nature of a subset of related electronic states. Our experiments provide a direct visualization of how in-situ spin reorientation drives changes in the electronic density of states of the Weyl fermion band structure. Combined with previous reports of massive Dirac fermions, flat bands, and electronic nematicity, our work establishes Fe3Sn2 as an interesting platform that harbors an extraordinarily wide array of topological and correlated electron phenomena. [ABSTRACT FROM AUTHOR]

The current study focuses on the effect of pressure on zinc oxide, ZnO, which is considered an essential element in several fields. In this research, the method of calculation has been used from the commencement to find the ZnO compound's structural and electrical characteristics at various pressure levels. It is found that the obtained results related to the crystal structure of the compound with phase (B4) Wurtzite agree well with previous theoretical and experimental findings. In addition, the electronic properties showed that ZnO has a direct gap of 0.68 eV, and the density of states showed that the3d position of the zinc atom significantly contributed to building the density of the electronic states of the compound, followed by the P-terminal of the oxygen atom. As it became clear to us that changing the pressure applied to the oxide ZnO increases the value of its energy gap, while the pressure value of 13.38 GPa is the crystal transition point from phase (B4) to (B1). [ABSTRACT FROM AUTHOR]

Mg2+‐Mo6+‐Al3+‐MoO42−‐Layered double hydroxides (LDHs) materials were successfully prepared via a hydrothermal method by doping Mo6+ in hydroxide laminates and inserting MoO42− to replace the interlayer anions of LDHs materials. The samples were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared spectrometer (FTIRS) and ultraviolet‐visible spectrophotometer (UV). The electronic density of states was calculated using the density functional theory (DFT) of Vienna Ab‐initio Simulation Package (VASP). The effects of Mo6+ and MoO42− on the structure, morphology, electronic structure and photocatalytic performance of Mg2+‐Al3+‐LDHs were systematically studied. The conditions for phenol degradation by Mg2+‐Mo6+‐Al3+‐MoO42−‐LDHs were optimized by single factor analysis and response surface methodology. The results show that the MoO42− anion reduces the band gap width and thus enhances the absorption of low‐energy photons. The interaction between cations and anions enhances the photocatalytic performance. When the dosage of Mg2+‐Mo6+‐Al3+‐MoO42−‐LDHs was 0.03 g, the temperature was 40 °C and the visible light irradiation was 15 min, the removal rate of phenol reached 94.76 %. [ABSTRACT FROM AUTHOR]

Thin films of amorphous BaTiO3 (a-BTO) were grown by spin coating technique on a glass substrate and annealed at different temperatures, from 300 to 500 °C, with a step of 50 °C. The samples were characterized structurally by X-ray diffraction (XRD), where broadband around 25° indicates the amorphous formation in all the thin films. The optical properties of the a-BTO thin films were determined by transmittance and reflectance UV-Visible spectroscopy. The optical responses were fit using Lorentz and Lorentz-Tauc classical models to determine the complex dielectric function. In addition, the photoluminescence (PL) of the glass and the a-BTO/glass system was also measured to observe the antireflective capacity of the a-BTO thin film as a function of the calcination temperature. To understand the experimental structural results ab-initio molecular dynamic calculation of 2x2x2 BTO supercell was utilized, while the electronic density of state and the complex dielectric function were obtained using Density Functional Theory (DFT). A comparison between the experimental and theoretical results is presented and discussed. [ABSTRACT FROM AUTHOR]

Rare earth noble metals compounds have a variety of physical properties, such as heavy fermions, topological, superconductivity, and so on. In this paper, the cohesive energy, mechanical, electrical, and magnetic properties of REAuBi2 (RE=La-Pr, Sm) and the mechanical properties of REAu (RE=La-Pr, Sm) were studied by first-principles calculations. The calculated cohesive energies of REAuBi2 are negative, indicating the stable structures of REAuBi2. The comparison between the mechanical properties of REAuBi2 and REAu, including the bulk modulus, shear modulus, Young's modulus, and Poisson's ratio, under ideal conditions is carried out. Electronic density of states, band structure, and phonon spectrum of REAuBi2 are also studied and discussed. LaAuBi2 alloy is in the paramagnetic state, while PrAuBi2 and SmAuBi2 alloys are in antiferromagnetic order obtained by the results of Birch–Murnagha equation fitting of cell volume and energy. [ABSTRACT FROM AUTHOR]

Pioneering of condensed matter physics relates to various factors of electronic correlations. Exploring new materials, always achieve important roles to develop the understanding of magnetism in correlated matter. Rare-earth-based compounds especially Cerium-based inter-metallics display different types of interesting properties and the reason behind these fascinating properties is the strongly correlated nature of these materials. In broadening our level of understanding on correlated materials especially on low temperatures, we aim to set a report on the compound of CeRuAl. Physical properties (magnetic, transport and electronic) of CeRuAl are measured for the temperature ranges 400 K to 0.5 K and in the magnetic field up to 7 T. It is observed that the Sommerfeld coefficient, which is calculated from the measurements of heat capacity, has the value of γ = 62 mJ/mol K2. At temperature 1.1 K, this compound CeRuAl shows mixed valent behavior. At the lower temperature range (0.9 K to 0.4 K) with applied field up to 0.5 T, the superconductivity property is evident. Absence of quick rise in low-temperature resistivity indicates that the gap formation in the electronic density of states does not exist. [ABSTRACT FROM AUTHOR]

We present the design and construction of a laboratory apparatus that provides advanced undergraduates with hands-on observations of electron quantum tunneling and the electronic density of states of various materials. The instrument is inspired by the scanning tunneling microscope (STM), but its implementation is simplified by limiting the tip motion to the single dimension along the tip-sample separation (z-axis); we refer to the device as the z-axis tunneling microscope (ZTM). Students are able to use the ZTM to measure electron tunneling probability as a function of barrier width, estimate relative material work functions, and observe differences in local electronic structure among metals, semimetals, and semiconductors. We share results obtained by third-year undergraduate physics students using the instrument for their final projects in an advanced instructional lab course. [ABSTRACT FROM AUTHOR]

The electronic and electrophysical properties of mono- and bilayer films of single-walled carbon nanotubes (SWCNTs) located on various types of substrates including substrates in the form of films of crystalline silicon dioxide SiO2 with space symmetry groups P42/mnm and P3121 are studied. It is established that the substrate plays an important role in the formation of the profile of electronic density of states of SWCNT films. It is found that due to the substrate, the quantum capacitance of SWCNT films increases by a factor from 1.6 to 2.2 when a voltage of more than 1 V is applied. It is shown that the presence of a substrate leads to a change in the electrical resistance of monolayer films from 2 to 17%. The electrical resistance of a bilayer film in the presence of a substrate remains practically unchanged in both directions of current transfer and is equal to ~6.4 kΩ, the minimum allowable value for SWCNTs. [ABSTRACT FROM AUTHOR]

According to the importance of electron–phonon interaction, we present an ab initio study of the electron–phonon coupling constant of two superconducting elements of periodic table. These values were calculated using density functional perturbation theory for uranium and lutetium, which are not available in the literatures. The electronic density of states peak that is around the Fermi energy and the sharp peaks in phonon dispersion curve are larger in magnitude for uranium, so the electron–phonon interaction in uranium is higher than that in lutetium. Then, we constructed a model by machine learning approach for 28 superconducting elements of the periodic table and chose the Debye and superconducting transition temperatures as descriptors features, to predict the electron–phonon coupling constants for uranium and lutetium. The absolute (relative) errors between the predicted by machine learning algorithm and density functional theory results of electron–phonon coupling constants are 0.01 (2%) and 0.13 (15%) for uranium and lutetium, respectively. This shows the power of the machine learning approach, which gives the results consistent with the density functional theory's results. [ABSTRACT FROM AUTHOR]

We investigate the role of magnetic impurities in the barrier region in enhancing the torque transferred to the free ferromagnet layer in a non-collinear model tunnel junction. The tunnel junction is modeled using the non-equilibrium Green's function formalism within the tight-binding approximation. The position of the impurity which is described by the single impurity Anderson model is found to have a profound impact on the trends observed in the spin transfer torque. The parallel ( T ∥ ) torque is observed to have a switch on-off step-like bias behavior while the perpendicular ( T ⊥ ) torque exhibits a change in sign between the switch-on bias voltages. The spin transfer torque is found to be dramatically enhanced when the impurity is positioned at the interface of a five-layer barrier which is three orders of magnitude larger even at temperatures as high as 200 K. With this formulation the effect of Coulomb repulsion at the impurity site on the torque could be deduced and the obtained results are explained in terms of the region-wise electronic density of states in the junction. [ABSTRACT FROM AUTHOR]

Single crystalline BaMnSb2 is considered as a 3D Weyl semimetal with the 2D electronic structure containing Dirac cones from the Sb sheet. We report experimental investigation of low-temperature cleaved BaMnSb2 surfaces using scanning tunneling microscopy/spectroscopy and low energy electron diffraction. By natural cleavage, we find two terminations: one is Ba (above the orthorhombically distorted Sb sheet) and another Sb2 (at the surface of the Sb/Mn/Sb sandwich layer). Both terminations show the 2 × 1 surface reconstructions, with drastically different morphologies and electronic properties, however. The reconstructed structures, defect types and nature of the electronic structures of the two terminations are extensively studied. The quasiparticle interference (QPI) analysis is conducted at the energy range between −2 V and 2 V, although no interesting states are observed near the Fermi level, the surface-projected electronic band structures strongly depend on the surface termination above 1.6 V. The existence of defects can greatly modify the local density of states to create electronic phase separations on the surface in the order of tens of nm scale. Our observation on the atomic structures of the terminations and the corresponding electronic structures provides critical information towards an understanding of topological properties of BaMnSb2. [ABSTRACT FROM AUTHOR]

Icosahedral quasicrystals (QCs) have a glass‐like, low thermal conductivity because of their complex crystal structures, and a moderate power factor because of deep pseudogap formation in their electronic density of states (DOS) at the Fermi level originating from icosahedral symmetry and covalent bonding nature. These features are beneficial for high‐performance thermoelectric materials. Densified bulk samples of icosahedral Al–Pd–Re–Fe QCs are synthesized by arc‐melting, annealing, and spark plasma sintering methods. It is found that a 2/1‐approximant crystal (AC) can be produced by higher Fe substitution [Al71Pd20(Re1–xFex)9 (x≥0.75)]. The thermoelectric properties of Al71Pd20(Re1–xFex)9 (where x = 0, 0.2, 0.4, 0.65, 0.7, and 0.75) are evaluated between 373 and 973 K. Fe substitution enhances the power factor and reduces the phonon thermal conductivity by a concept of "weakly bonded rigid heavy clusters" (WBRHCs) and an increase in the carrier concentration, enhancing the dimensionless figure of merit (zT). The 2/1‐AC phase has a much higher electrical conductivity and a moderate Seebeck coefficient in the mid‐temperature region due to a considerable increase in carrier concentration; this results in the highest power factor of 900 μW m−1 K−2, and zT value for the 2/1‐Al−Pd−Re−Fe AC is 0.26 at 573 K. [ABSTRACT FROM AUTHOR]

The crystal structure of the γ‐brass type Cu5+δCd8‐δ (‐1.0≤δ≤0.1) in the Cu−Cd binary system has been analyzed by powder and single crystal X‐ray diffraction. All the compounds crystallize in the cubic space group I4‾3m (217). Mixing of Cu with Cd leads to a significant phase width. At the limiting composition, a previously unreported ordered compound Cu4Cd9 is formed. The structure of all compounds is described by a 26‐atom γ‐cluster. Electronic structure calculations on the model structure built according to the ordered "Cu4Cd9", show the presence of a pseudo‐gap at the Fermi level in the electronic density of states, which is consistent with other γ‐brass type phases. However, the site preference of Cu and Cd atoms is different from the other reported γ‐brass type structures in the Zn‐ and Cd‐rich phases. To address the "coloring problem", a series of model structures were constructed with the composition Cu4Cd9 and their total energies were compared with first‐principle calculations using ABINIT code. LOBSTER package was implemented to extract the bonding information by crystal orbital Hamilton population calculations. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 (CO2RR) to value‐added chemicals is an effective way to harvest renewable energy and utilize carbon dioxide. However, the electrocatalysts for CO2RR suffer from insufficient activity and selectivity due to the limitation of CO2 activation. In this work, a Ni‐doped Bi nanosheet (Ni@Bi‐NS) electrocatalyst is synthesized for the electrochemical reduction of CO2 to HCOOH. Physicochemical characterization methods are extensively used to investigate the composition and structure of the materials. Electrochemical results reveal that for the production of HCOOH, the obtained Ni@Bi‐NS exhibits an equivalent current density of 51.12 mA cm−2 at −1.10 V, which is much higher than the pure Bi‐NS (18.00 mA cm−2 at −1.10 V). A high Faradaic efficiency over 92.0 % for HCOOH is achieved in a wide potential range from −0.80 to −1.10 V, and particularly, the highest efficiency of 98.4 % is achieved at −0.90 V. Both experimental and theoretical results reveal that the superior activity and selectivity are attributed to the doping effect of Ni on the Bi nanosheet. The density functional theory calculation reveals that upon doping, the charge is transferred from Ni to the adjacent Bi atoms, which shifts the p‐orbital electronic density states towards the Fermi level. The resultant strong orbital hybridization between Bi and the π* orbitals of CO2 facilitates the formation of *OCHO intermediates and favors its activation. This work provides an effective strategy to develop active and selective electrocatalysts for CO2RR by modulating the electronic density state. [ABSTRACT FROM AUTHOR]

The structure, equation of state and transport properties of warm dense nitric oxide (NO) were investigated in wide density and temperature ranges by ab initio molecular dynamics simulations. Both the Perdew–Burke–Ernzerhof (PBE) and the strongly constrained and appropriately normed functional with revised Vydrov–van Voorhis nonlocal correlation (SCAN−rVV10) functionals were used in the simulations, and the pressures predicted by the SCAN−rVV10 functional were found to be systematically lower than those predicted using PBE and experimental data along the shock Hugoniot curve. Along the Hugoniot curve, as density increased, we found that the system transformed towards a mixture of atomic nitrogen and oxygen liquids with molecular NO that remained present up to the highest densities explored. The electrical conductivity along Hugoniot indicated that nonmetal to metal transition had taken place. We also calculated the electrical and thermal conductivities of nitric oxide in the warm dense matter regime, and used them to compute the Lorentz number. In addition, we also report the electronic density of states. [ABSTRACT FROM AUTHOR]

A high-throughput computational method is used to predict 39 new superconductors in the Ti-based M 2 AX phases, and the best candidates are then studied in more detail using density functional theory electron–phonon coupling calculations. The detailed calculations agree with the simple predictions, and Ti 2 AlX (X: B, C and N) materials are predicted to have higher values of T c than any currently known hexagonal M 2 AX phases. The electronic states at the Fermi level are dominated by the Ti 3d states. The choice of X (X: B, C and N) has a significant impact on the electronic density of states but not on the phonon characteristics. The electron–phonon coupling parameter for Ti 2 AlX (X: B, C and N) was determined to be 0.685, 0.743 and 0.775 with a predicted T c of 7.8 K, 10.8 K and 13.0 K, respectively. [ABSTRACT FROM AUTHOR]

Half-metallic ferromagnetic full Heusler alloy NiFeMnSn is a promising material in spintronic device fabrication as it carries high spin polarization and high Curie temperature (Tc = 405 K). Understanding electronic excitations in a spin-polarized band structure is essential for the further use of this material in spin-based devices and to optimize the spin-dependent electronic structure in related compounds. In this Letter, we report electronic Raman scattering of NiFeMnSn with spectral signatures at a higher wavenumber than expected from the calculated phonon modes of the system. Temperature-dependent Raman spectroscopy demonstrates a non-monotonic behavior of the Raman shift with temperature across Tc. The orbital resolved electronic density of states and electronic band structure for both spin channels of the system, as obtained from the first principles density functional theory calculations, suggest that the observed Raman signatures originate from the Fe d orbital and its splitting due to the crystal field near the Fermi level. Furthermore, a strong magnetic field dependence of the spectral profile is observed. The study not only exhibits electronic Raman scattering in a Heusler alloy compound, which was unexplored to date, but also establishes Raman scattering as a promising probe to study the orbital-resolved partial density of states in the band structure near the Fermi level of a Heusler alloy. [ABSTRACT FROM AUTHOR]

We provide a comparative first-principles investigation of the structural, electronic, vibrational, and thermodynamic properties of the full Heusler compounds, cubic Fe2NiAl, and tetragonally distorted Co2NiAl. In both cases, we find the inverse Heusler structure to be in close competition with a layered arrangement of the elements, which breaks cubic symmetry and is accompanied by significant absolute values for the magnetocrystalline anisotropy energy. While for Fe2NiAl the layered arrangement is predicted as a new ground state, we show evidence that it might become dynamically stable around room temperatures also for Co2NiAl. We identify in both systems subtle differences in the electronic and vibrational density of states between the different structures, which might be related to their particular stability. [ABSTRACT FROM AUTHOR]

The crystal structure prediction algorithm has been performed using the swarm-intelligence-based CALYPSO method combined with density functional theory. The P4/mmm phase and R-3c phase are found for potential superhard OsN4, energetically much superior to the previously proposed Pbca-type structure. It is confirmed that the stable ground-state structure of OsN4 is the P4/mmm phase. More importantly, the phase transformation is firstly found from the P4/mmm phase to the R-3c phase at nearly 65.3 GPa. And the two phases of the OsN4 not only have the high bulk and shear modulus but also the low Poisson's ratio. This suggests that the OsN4 compound has the potential to be a low-compression material. According to a detailed analysis of the density of states and electronic local functions, it is revealed that the covalent bonding of Os–N and N–N are responsible for their structural stability and high hardness. [ABSTRACT FROM AUTHOR]

Silicene, together with copper or nickel, is the main component of electrodes for solar cells, lithium-ion batteries (LIB) and new-generation supercapacitors. The aim of this work was to study the electronic properties and geometric structure of "silicene–Ni" and "silicene–Cu" systems intended for use as LIB electrodes. The densities of electronic states, band structures, adhesion energies and interatomic distances in the silicene–(Cu, Ni) systems were determined by ab initio calculations. Silicene on a copper substrate exhibited temperature stability in the temperature range from 200 to 800 K, while on a nickel substrate, the structure of silicene was rearranged. Adsorption energies and bond lengths in the "silicene–Cu" system were calculated in the range of Li/Si ratios from 0.125 to 0.5. The formation of the Li2 isomer during the adsorption of lithium in a ratio to silicon of 0.375 and 0.5 was observed. Silicene was found to remain stable when placed on a copper substrate coated with a single layer of nickel. The charge redistribution caused by the addition of a nickel intermediate layer between silicene and a copper substrate was studied. [ABSTRACT FROM AUTHOR]

The formation and the stability of a unique intermetallic phase Rh2Cd5 (2:5) that adopts a defect In3Pd5 structure type, has been addressed on the basis of electronic structure calculation and chemical bonding approach. The crystal structures of three closely related phases {RhCd, Rh2Cd5 and Rh3Cd5−δ (δ ∼ 0.56)} in the Rh–Cd binary system are compared. Electronic structure calculations for all these phases reveal that a state-deficient region or pseudogap is opened up near the Fermi level in the electronic density of states. [ABSTRACT FROM AUTHOR]

I present an analysis of the temperature dependence of the electrical resistivity of δ-phase plutonium alloys. I find that the resistivity is mainly proportional to the electronic Kondo heat capacity, with an additional term, linear in temperature, that is correlated with the absolute low-temperature resistivity. This indicates a so-called Mooij correlation, which is often observed in disordered materials. These two terms can be understood together as different contributions to the resistivity, proportional to their respective electronic densities of states. The method presented in this paper provides a simple means of quantifying such resistivity data, and the data for a large number of δ-phase plutonium alloys have been fitted with only four parameters each. [ABSTRACT FROM AUTHOR]

Poly‐ether‐ether‐ketone (PEEK) is a widely used and versatile polymer. Here, we use ellipsometry to determine the wavelength‐dependent optical properties of PEEK before and after the surface is modified by plasma immersion ion implantation (PIII), a technique that renders the surface hydrophilic and bio‐active. Lorentz and Gaussian oscillator models are used to fit the data for extraction of the optical constants and the dielectric function. The effect of PIII, even for short treatment times, changes the optical properties of PEEK, indicative of an amorphisation of the initial semicrystalline structure that broadens the electronic density of states distribution. The progressive changes in the optical properties with treatment time allow assessment of colour changes and estimation of ion dose in the PIII process. [ABSTRACT FROM AUTHOR]

In a transformer, the insulation materials will produce different dissolved gases due to various faults in the operation of the transformer, in which C2H2, CH4, and H2 are the main dissolved gases. In this study, the adsorption characteristics of the above three gases on the SnO2–GeSe monolayer surface were discussed and analyzed based on the density functional theory. The adsorption energy, transfer charge, geometric structure parameters, electronic density of states, electronic local function, charge difference density, and recovery time were calculated and compared to characterize the gas-sensing adsorption mechanism. The results showed that the SnO2–GeSe monolayer exhibited good adsorption capacity, selectivity, and repeatability for the three characteristic dissolved gases. After adsorbing CH4 gas molecules, the conductivity of the SnO2–GeSe monolayer decreased. After adsorbing C2H2 and H2 gas molecules, the conductivity of the SnO2–GeSe monolayer increased. Therefore, the SnO2–GeSe monolayer has great application potential in the real-time monitoring of dissolved gases in insulating materials, which may become a new type of resistive gas sensor. [ABSTRACT FROM AUTHOR]

Suppression of phonon transports is a key requirement to achieve high thermoelectric performance, which has been often realized by doping an element to enhance the phonon scattering. However, detailed origins behind the dopant-induced low lattice thermal conductivity (κ ph) have not yet been comprehensively understood. Here, we demonstrate a κ ph reduction mechanism induced by the phonon softening in the element-doped Fe 2 VAl thermoelectric Heusler compounds. Inelastic X-ray scattering experiments revealed that overall optical phonons are softened with increasing Ti-doping concentration in marked contrast to the Ta-doped Fe 2 VAl. By means of photoelectron spectroscopy, we found that the observed phonon softening is originating from the rigid-band shift of the electronic density of states and the consequent deviation of the pseudo-gap position from the Fermi level, which causes the energetic instability of the electronic system. This instability is accompanied by the reduction of the filled bonding states, giving rise to the phonon softening. This mechanism of κ ph reduction caused by the close correlation between electronic and phononic systems will shed new light on achieving low- κ ph and thereby developing unconventional high-performance thermoelectric materials. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, the effects of pressure on the formation enthalpy, elastic constants, elastic modulus, electronic density of states and elastic anisotropy of Fe(WB) 2 , Co(WB) 2 , Ni(WB) 2 borides were investigated by first-principles calculation. The plasticity of Fe(WB) 2 in 90 GPa is due to the other two, while the strength and hardness of Co(WB) 2 are better and all three borides show anisotropy at 0–90 GPa. Ab initio molecular dynamics was used to predict the structural stability properties of three borides at 1500 K. The quasi-harmonic approximation and the quasi-static approximation were respectively used to study the thermodynamic properties and the mechanical properties at finite temperatures of borides. At 1500 K, the Young's modulus of the three borides from largest to smallest is Fe(WB) 2 (468.02 GPa) > Co(WB) 2 (461.29 GPa) > Ni(WB) 2 (417.41 GPa). In addition, calculations of optical properties show that Ni(WB) 2 has a high reflectivity in the low energy range. [ABSTRACT FROM AUTHOR]

Using density functional theory (DFT), geometric optimizations were performed on the supercell systems of undoped cassiterite and 24 types of doped cassiterite with metals such as Sc, Ti, V, etc. The lattice constants, band structures, and electronic density of states (DOS) were calculated to investigate the crystal structure and electronic properties of cassiterite. The results indicate that the presence of impurity defects leads to varying degrees of distortion in the lattice angles and unit cell of cassiterite crystal. Doping with Ti and Al increases the semiconductor band gap of cassiterite, while other impurity-doped cassiterite decreases the band gap. The impurity-doped cassiterite band gap gradually decreases with increasing atomic number, exhibiting semiconductor-to-metal transition in the doped cassiterite. The overall DOS of cassiterite doped with Nb, Mo, Ta, W, As, Sb and Bi shifts to the direction of low energy, and the oxidation capacity of cassiterite is enhanced. [ABSTRACT FROM AUTHOR]

TiO2 nanoparticles (NPs) are nowadays considered fundamental building blocks for many technological applications. Morphology is found to play a key role with spherical NPs presenting higher binding properties and chemical activity. From the experimental point of view, the characterization of these nano-objects is extremely complex, opening a large room for computational investigations. In this work, TiO2 spherical NPs of different sizes (from 300 to 4000 atoms) have been studied with a two-scale computational approach. Global optimization to obtain stable and equilibrated nanospheres was performed with a self-consistent charge density functional tight-binding (SCC-DFTB) simulated annealing process, causing a considerable atomic rearrangement within the nanospheres. Those SCCDFTB relaxed structures have been then optimized at the DFT(B3LYP) level of theory. We present a systematic and comparative SCC-DFTB vs DFT(B3LYP) study of the structural properties, with particular emphasis on the surface-to-bulk sites ratio, coordination distribution of surface sites, and surface energy. From the electronic point of view, we compare HOMO-LUMO and Kohn-Sham gaps, total and projected density of states. Overall, the comparisons between DFTB and hybrid density functional theory show that DFTB provides a rather accurate geometrical and electronic description of these nanospheres of realistic size (up to a diameter of 4.4 nm) at an extremely reduced computational cost. This opens for new challenges in simulations of very large systems and more extended molecular dynamics. [ABSTRACT FROM AUTHOR]

Provided the initial state, the Runge-Gross theorem establishes that the time-dependent (TD) external potential of a system of non-relativistic electrons determines uniquely their TD electronic density, and vice versa (up to a constant in the potential). This theorem requires the TD external potential and density to be Taylor-expandable around the initial time of the propagation. This paper presents an extension without this restriction. Given the initial state of the system and evolution of the density due to some TD scalar potential, we show that a perturbative (not necessarily weak) TD potential that induces a non-zero divergence of the external force-density, inside a small spatial subset and immediately after the initial propagation time, will cause a change in the density within that subset, implying that the TD potential uniquely determines the TD density. In this proof, we assume unitary evolution of wavefunctions and first-order differentiability (which does not imply analyticity) in time of the internal and external force-densities, electronic density, current density, and their spatial derivatives over the small spatial subset and short time interval. [ABSTRACT FROM AUTHOR]

A novel sp2-sp3 hybridized orthorhombic BC2N (o-BC2N) structure (space group: Pmm2, No. 25 ) is investigated using first-principles calculations. O-BC2N is constructed from multi-layers of C sandwiched between two layers of BN along the c axis; this structure contains sp2- and sp3-hybridized B-C, C-C, and C-N bonds. The structural stability of o-BC2N is confirmed based on the calculation results for elastic constants and phonon dispersions. On the basis of the semi-empirical microscopic model, we speculate that the o-BC2N compound is a potential superhard material with a Vickers hardness of 41.2 GPa. Calculated results for electronic band structures, density of states (DOS) and partial DOS (PDOS) show that the o-BC2N crystal is metallic. The conducting electrons at the Fermi level are mostly from the 2p orbits of sp2-hybridized B4, N1, and Ci (i¼2, 3, 4, 6, 7, 8) atoms, with slight contribution from the sp3-hybridizd B2 atoms. Furthermore, the calculated electron orbits of the o-BC2N crystal demonstrate that the 2p orbits of the sp2-hybridized atoms overlapped and formed π bonds. The electrons can conduct through the π bonds along the orientation parallel to the [100] and [010] directions in different layers, and the basal planes were formed by B2-C3-C4 blocks, indicating that the o-BC2N possesses the fascinating electronic property of linearplanar metallicity. [ABSTRACT FROM AUTHOR]

We present an integration scheme for optimizing the orbitals in numerical electronic structure calculations on general molecules. The orbital optimization is performed by integrating the Helmholtz kernel in the double bubble and cube basis, where bubbles represent the steep part of the functions in the vicinity of the nuclei, whereas the remaining cube part is expanded on an equidistant threedimensional grid. The bubbles' part is treated by using one-center expansions of the Helmholtz kernel in spherical harmonics multiplied with modified spherical Bessel functions of the first and second kinds. The angular part of the bubble functions can be integrated analytically, whereas the radial part is integrated numerically. The cube part is integrated using a similar method as we previously implemented for numerically integrating two-electron potentials. The beavior of the integrand of the auxiliary dimension introduced by the integral transformation of the Helmholtz kernel has also been investigated. The correctness of the implementation has been checked by performing Hartree-Fock self-consistent-field calculations on H2, H2O, and CO. The obtained energies are compared with reference values in the literature showing that an accuracy of 10-4 to 10-7 Eh can be obtained with our approach. [ABSTRACT FROM AUTHOR]

We investigate the coupled electron-nuclear dynamics in a model system showing a conical intersection (CoIn) between two excited state potential energy surfaces. Within the model, a single electron and nucleus move in two dimensions in an external static field. It is demonstrated that the nuclear density conserves its initial Gaussian shape when directly passing the CoIn, whereas the electronic density remains approximately constant. This is in sharp contrast to the picture which evolves from an analysis within the basis of adiabatic electronic states. There, dramatic changes are seen in the dynamics of the different nuclear components of the total wave function. It is thus documented that, in the case of a highly efficient population transfer between the respective adiabatic states, neither the nuclear nor the electronic density is influenced by the existence of a CoIn. This is the case because the nuclear-electronic wave packet moves on the complete potential energy surface which changes its topology smoothly as a function of all particle coordinates. [ABSTRACT FROM AUTHOR]

We have performed a comparative first-principles study on the structural and electronic properties of the liquid Li1-xSix and Li1-xGex alloys over a range of composition from x = 0.09 to 0.50. Our calculations showed that Si and Ge atoms can exhibit very distinct local bonding characteristics as they were alloyed with the Li atoms in the liquid state, where Si atoms tended to form a variety of covalent bonding configurations while Ge atoms predominantly appeared as the isolated anions in the liquid alloys. These differences in bonding characteristics were reflected in their electronic density of states, in which the liquid Li1-xGex alloys have a lower degree of s-p hybridization with narrower distributions of the 3s and 3p states than the liquid Li1-xSix alloys. Our calculations also showed that the optical conductivities of these two liquid alloys can undergo a transition from the Drude-like metallic nature to the semiconductor-like character as the Si/Ge content increases from 0.09 to 0.22. However, as the Si/Ge content further increases to 0.50, the liquid Li1-xGex alloys may transit to exhibit the Drude-like metallic nature, while the liquid Li1-xSix alloys can still hold the semiconductor-like character. Moreover, our calculations revealed that the dc conductivities of these liquid alloys are predominantly determined by the number of total electronic states at the Fermi level. As the liquid Li1-xSix alloys are within the composition range between 0.20 and 0.50, the increment of the states at the Fermi level with increasing the Si content is nearly identical to the amount of the Li states decreased, leading to an almost unchanged number of total electronic states at the Fermi level. However, since Ge atoms do not favor forming covalent bonding in the liquid alloys to keep the Fermi level at a minimum of the density of states, the liquid Li1-xGex alloys would have more electronic states at the Fermi level and thereby higher dc conductivities than the liquid Li1-xSix alloys within the same composition range. [ABSTRACT FROM AUTHOR]

In the current era of escalating concerns over energy and water pollution, the quest for highly efficient semiconductor materials has emerged as a critical priority. In this context, semiconductor catalysts based on the M-N 4 structure constructed on carbon and nitrogen materials have garnered significant attention due to their uniform active sites, distinctive electronic properties, and exceptional redox activity. However, these catalysts often encounter commercial challenges such as unstable metal center atoms and unmanageable coordination numbers. While graphitic carbon nitride (g-C 3 N 4) based on stable tri-s-triazine aromatic heterocycles can effectively address these issues, there is a dearth of discussion on the electronic regulation mechanism of M-N 4 sites for g-C 3 N 4 -based catalysts. This review aims to provide a comprehensive overview of the configuration of M-N 4 sites on the g-C 3 N 4 substrate and to explore the influence of specific M-N 4 sites on the electronic state density of the g-C 3 N 4 substrate, thereby enhancing our understanding of the correlation between the electronic structure of the catalyst and its catalytic performance. Furthermore, we present several strategies for regulating the electron density of g-C 3 N 4 -based catalysts containing M-N 4 sites, including non-metal atom doping, the introduction of vacancies, and the creation of dual-atom catalysts (DACs), with the goal of optimizing the catalyst's performance and facilitating its practical application. Finally, we discuss the current challenges and potential future directions for g-C 3 N 4 -based catalysts containing g-C 3 N 4 sites, with the belief that this will offer theoretical guidance for the future design of efficient catalysts and contribute to their successful implementation. [ABSTRACT FROM AUTHOR]

• Atomistic models of IPG are developed employing the melt-quench process using AIMD simulations. • IRO is successfully reproduced in the obtained IPG model. • FSDP in S(q) carries the structure connectivity information. • Dangling bonds majorly contribute to the defect states in DOS. • Q 1 units dominate in the obtained model. Iron Phosphate glass (IPG) has recently gained interest for immobilizing high level nuclear wastes. In the current study, we report the first atomistic model of IPG developed by performing ab-initio molecular dynamics (AIMD) simulations on crystalline Fe 3 (P 2 O 7) 2 following the melt-quench procedure. The resulting structure is characterized at short and intermediate length scales. Although it is quite challenging to reproduce the intermediate range order (IRO) in small-scale AIMD simulated models, from the analysis of ring size distribution and neutron structure factor, it is found that the obtained model successfully exhibits the IRO. Furthermore, the electronic density of states (DOS) of the system is plotted, and the band gap region denotes the presence of dangling bond defects. The effects of different vacancies in the DOS are also studied. Apart from this, elastic and vibrational properties are also studied, and the results are compared with the available theoretical and experimental results. [ABSTRACT FROM AUTHOR]

The investigation focused on examining the structural, optical, elastic, and thermoelectric properties of the developing double perovskites Rb 2 NaTlZ 6 (Z = Cl, Br, and I). The cubic phase of the investigated halide double perovskites (HDPs) was confirmed, based on the tolerance factor (τ) metrics of 0.853, 0.845, and 0.835, respectively. The thermodynamic stability of HDPs was evidenced by the negative formation energies. The mechanical stability, ductility, and anisotropic characteristics of the material under investigation are determined by its elastic parameters. The existence of a direct band gap (E g) has been confirmed by density of states and electronic band gap calculations. The determined values for the band gap are 3.4, 2.6, and 2.1 eV, respectively. The current study centers on examining the absorption of light energy, refractive index, polarization, and optical loss across the complete energy spectra spanning between 0 and 10 eV. The spectral features revealed their appropriateness for photovoltaic energy systems due to the absorption unfolding within the UV spectrum. The thermoelectric properties, as assessed by using the BoltzTraP code, indicated that the highest ZT values obtained for both materials were 0.63, 0.63, and 0.71, respectively. Although these materials exhibit minimal optical absorption in the visible along with significant optical absorption in the ultraviolet region and possess a moderate ZT value, it is imperative to explore effective techniques for tuning the energy band gap to augment the thermoelectric and material's spectral properties. Therefore, this modification renders it more appropriate for experimental and practical utilization in the field of energy production. [ABSTRACT FROM AUTHOR]

We explore, through a first principle approach based on density functional theory, lithiated-silicon (Li-Si) surfaces and their intricate interactions with binders in lithium-ion batteries. A meticulous analysis of Li insertion in the Si-subsurface layer unveils crucial dynamics, including surface reconstructions, and structural changes in different Si facets (Si-110 and Si-111). The impact of lithium content and Si facet orientation on the binder adhesion strength demonstrates that increasing the number of subsurface Li atoms weakens adhesion. However, a strategic co-binding approach, in which polyvinyl alcohol (PVA) is associated with polyaniline (PANI), polyaniline functionalized PANI with boronic acid groups (B-OH_PANI) or polyvinylidene fluoride (β -PVDF), is revealed to be a decisive factor in stabilizing monomers on the surface. Advanced electronic structure analyses portray changes in the charge density distribution and electronic states due to Li insertion into the Si surfaces. Molecular dynamics simulations of bulk co-binder models provide a concrete visualization of the structural relaxations and bonding interactions at the Li-Si/co-binder interface. The insights derived from this study serve as a foundation for the design and development of cutting-edge lithium-ion battery materials. • Adhesion of co-binders to new active material surfaces. • Influence of lithiation on the optimal polymer/active material interface geometry. • Atomistic knowledge of binding to optimize the properties of Si/binder interfaces. [ABSTRACT FROM AUTHOR]

• The impact of atomic substitution on the properties of B2 crystals was investigated. • The impact of atomic arrangement on the properties of B2 crystals was examined. • The impact of atomic quantity on crystal properties was examined. • The impact of various substitution patterns on energy band distribution and electronic density of states is assessed. Grounded in research on B2 crystal structures, this study systematically substitutes the central 8 atoms with non-metallic Si atoms and metallic Fe atoms, exploring the resulting impacts on stress, magnetism, and energy across the entire crystal lattice. The positional permutations of these atoms are meticulously examined to elucidate their influence. Additionally, alterations in crystal parameters are analyzed through the lenses of energy band distribution and electronic density of states. Findings underscore that substituting non-metallic Si atoms with metallic Fe counterparts significantly increases stress, magnetism, and energy levels throughout the crystal lattice. Moreover, a positive correlation emerges between the quantity of replacements and the resulting stress levels, magnetic intensity, and energy. The arrangement of atoms demonstrates a substantial influence on material magnetism, with denser distributions yielding more pronounced effects on the overall system; individual arrangements are capable of increasing magnetism by approximately 23%. These insights are further validated by changes in energy band distribution and electronic state density, which show a continuous enhancement of metallic properties and reactivity as Si atoms are successively replaced by Fe atoms. This study introduces an innovative idea for enhancing material performance. [ABSTRACT FROM AUTHOR]

This report aims to investigate the structural, mechanical, optical, thermal, and electronic properties along with hardness of CuXO 3 (X = Al, In) perovskites for the first time by using first-principles calculations within the density functional theory (DFT). The geometry of the both structures have been optimized by using Broyden-Fletcher-Goldfarb-Shanno (BFGS) minimization technique and confirmed as the cubic structure with the space group of P m ‾ 3 m (No. 221). The studied lattice parameters of CuXO 3 (X = Al, In) closely resemble with previous theoretical and experimental results. Both the compounds of CuXO 3 (X = Al, In) under investigation are mechanically stable as the calculated elastic constants satisfy the Born stability criteria. The calculated value of Pugh's ratio, Poisson's ratio and Cauchy pressure confirm strong ductility behavior in contrast to brittleness of these compounds. The elastic anisotropy calculations confirm the anisotropic nature in CuAlO 3 in contrast to isotropic nature as observed in CuInO 3. CuAlO 3 is predicted to be harder than that of CuInO 3. CuInO 3 shows the highest machinability index among studied compounds. The electronic band-structure and density of states ensure semiconducting nature in CuAlO 3 whereas, CuInO 3 reveals metallic nature. The investigation of optical properties reveals the prospective application of the entitled substances in a wide range of electronic and optoelectronic device uses. The title compounds could be used as thermal barrier coating materials (TBC) for exhibiting low thermal conductivity. [Display omitted] [ABSTRACT FROM AUTHOR]

Two-dimensional materials have emerged as promising candidates for service in miniaturized electronic and optoelectronic devices due to their exceptional properties and atomically thin dimensions. Here we study the structural, electronic, and optical properties (e.g., the absorption coefficient and optical conductivity) of 2D AlOF using density functional theory. Our 2D AlOF monolayer is dynamically stable. The TDOSs and BS calculations show that this monolayer would be an insulator. The total density of states and electronic band structures of AlOF are accomplished under different magnetic orders employing the DFT+U (U=1 and 7 eV) Hubbard approach. We demonstrate that the band gap energy E g of the AlOF layer can be controlled by applying different magnetic orders, e.g., non-magnetic (NM), Ferromagnetic (FM), and Antiferromagnetic (AFM). The spin-up and spin-down band structures show that the band gap nature can be modified by changing U from 1 eV to 7 eV. The effect of FM and AFM on the nature of the band gap energy is the same. Besides, the AlOF compound has a high absorption coefficient in the 5.23-30 eV region. This AlOF compound appears transparent once the incident light's frequency surpasses the plasma frequency (30.00 eV). The significance of the absorption coefficient and gap energy indicate that this substance will perform well in optoelectronic devices. • Our 2D AlOF single-layer structure is dynamically stable. • The TDOSs and BS calculations show that this 2D sheet is a wide-band-gap semiconductor. • Our spin-up and spin-down computations demonstrate that our monolayer is non-magnetic. • The influence of FM and AFM with the DFT+U approach on the nature of the band gap energy is studied. • Our compound appears transparent once the incident light's frequency surpasses the plasma frequency (30.00 eV). [ABSTRACT FROM AUTHOR]

In this work, we have performed a theoretical calculation to investigate the structural, mechanical, electronic, lattice dynamics, and thermodynamic properties of Ta T Si (T = Rh, Os, Ir) within the full potential linearized augmented plane wave method. Both (a) TaRhSi and (b) TaIrSi exhibit a reduction in the density of states at the Fermi energy, resulting from a pseudogap-like feature nearby the Fermi energy. This reduction is likely to suppresses the superconductivity of TaRhSi and TaIrSi. In contrast, (c) TaOsSi demonstrates a relatively higher density of states at the Fermi energy, which could account for its superconducting properties. [Display omitted] • The full potential linearized augmented plane wave method was used. • The elastic mechanical, electronic, thermodynamic, and lattice dynamics properties. • of TaRhSi and TaOsSi, and TaIrSi, were predicted. • TaRhSi and TaIrSi exhibit a pseudogap-like feature in the density of states nearby. • the Fermi energy. • The elastic anisotropy of TaRhSi and TaOsSi, and TaIrSi were observed. We have performed a theoretical calculation, based on density functional theory, to investigate the structural, mechanical, electronic, lattice dynamics, and thermodynamic properties of Ta T Si (T = Rh, Os, Ir) within the full potential linearized augmented plane wave method. The calculated values of the lattice constant and unit cell volume are in excellent agreement with the available experimental data. The mechanical stability is substantiated by our calculated elastic constants, while the mechanical properties are subsequently derived. The results indicate that the compounds are ductile materials, except for TaRhSi which exhibits quasi-ductile behavior; however, all of them exhibit elastic anisotropy. In addition, the electronic density of states of the Ta T Si (T = Rh, Os, Ir) compounds reveal that all these materials have a metallic character. Moreover, the dynamical stability is confirmed by our calculated phonon spectra. Finally, we present temperature-dependent thermodynamic properties including free energy, internal energy, entropy, and heat capacity. [ABSTRACT FROM AUTHOR]

The density function theory (DFT) with GGA and PBE was employed to determine the structural, electrical, and optical characteristics of pure and Cu doped AgZnF 3 type Fluro-perovskite. The structural properties of composite are calculated in realistic agreement with those testified in the literature. The band gap of the hybrid AgZnF 3 is small and indirect. AgZnF 3 contained a calculated band width of 1.52 eV. AgZnF 3 's total electronic properties were principally controlled by the Zn atom, whereas the Zn-d state and the F-p state had a minor impact on its partial electronic properties and state density. Cu doping modified AgZnF 3 's electrical band structure by narrowing the band gap. With increasing doping concentrations, the partial densities of states, which are likewise impacted by doping concentrations decreased. This material is appropriate for a variety of applications due to the improvement in optical characteristics and decrease in the band gap. [ABSTRACT FROM AUTHOR]

The first-principles calculations were employed to investigated the interaction of between CeO 2 (1 1 1) and SiO 2 (0 0 1) planes to understand the polishing mechanism. [Display omitted] The adhesion and electronic characteristics of the CeO 2 /SiO 2 heterostructures were examined via the first-principles method. The influence of surface termination of CeO 2 and SiO 2 on the interfacial properties were carefully examined. The structural and electronic characteristics such as densities of states, charge redistribution, charge transfer, and work function are discussed to explain the influence on the interface. The CeO/OSi interfacial configuration exhibited the highest energy favorability among the four different CeO 2 /SiO 2 interface structures. Moreover, the influence of rare earth dopant at the interface on adhesion work was also studied. All considered rare earth impurities (La, Pr, or Nd) on Ce-site at the interface lead to contrasting effects on interfacial interaction within different CeO 2 terminations. Our findings offer valuable insights for formulating high-performance CeO 2 abrasives for quartz glass polishing. [ABSTRACT FROM AUTHOR]

The recent discovery of superconductivity behavior in the mother BiS 2 -layered compounds has captivated the attention of several physicists. The crystal structure of superconductors with alternate layers of BiS 2 is homologous to that of cuprates and Fe-based superconductors. The full-potential linearized augmented plane-wave (FP-LAPW) technique was utilized to investigate the electronic structures and density of states in the vicinity of the Fermi energy of SrFBiS 2 and BaFBiS 2 compounds under the electron carriers doping. The introduction of electron doping (carries doping) reveals that the host compounds SrFBiS 2 and BaFBiS 2 exhibit features indicative of superconductivity. This carrier doping of SrFBiS 2 and BaFBiS 2 compounds (electron-doped) has a significant impact on the lowest conduction states near the Fermi level for the emergence of the superconducting aspect. The electron doping modifies and induces changes in the electronic structures with superconducting behavior in (Ae) 1.7 FBi S 2 (Ae = Sr , Ba) compounds. A Fermi surface nesting occurred under the modification of electrons (carriers) doping in the host compounds SrFBiS 2 and BaFBiS 2. Furthermore, the optical characteristics of the carrier-doped SrFBiS 2 and BaFBiS 2 compounds are simulated. Due to the anisotropic behavior, the optical properties of these materials based on BiS 2 demonstrate a pronounced polarization dependency. The starting point at zero photon energy in the infrared region is elucidated by considering the Drude features in the optical conductivity spectra of SrFBiS 2 and BaFBiS 2 compounds, when the electron carriers doping is applied. It was clearly noticed that the spin-orbit coupling (SOC) influences the electronic band structures, density of states, Femi surface, and optical features because of the heavy Bismuth atom, which may disclose fascinating aspects. Further, we conducted simulations to assess the thermoelectric properties of these mother compounds. The two BiS 2 -layered compounds could be suitable for practical thermoelectric purposes and are highlighted through assessment of electrical conductivity, thermal conductivity, Seebeck coefficient, and power factor. As a result, we propose that the mechanisms of superconducting behavior in BiS 2 family may pave new avenues for investigating the field of unconventional superconductivity. It may also provide new insights into the origin of high-T c superconductivity nature. [Display omitted] • Electronic structure showed a shift of the lower conduction states below E F versus electron doping in SrFBiS 2 and BaFBiS 2. • The Fermi surface topology illustrated a nesting at the wave vector (π , π , 0) upon the electrons doping effect. • The optical anisotropy is remarkable in all optical spectra upon the electrons doping effect. • Metallicity with Drude-model emerged at incident photon energies change from zero energy to IR range upon electrons doping. • These BiS 2 layered compounds could be useful for new superconductivity and thermoelectric applications. [ABSTRACT FROM AUTHOR]

Summary: In this paper, the crystal structures, thermodynamic stability, electronic densities of states, band structures, and optical properties of the nontoxic Pb‐free vacancy ordered double perovskites halides X2TeY6 (X = Cs, Rb, and Y = I, Br, Cl) were investigated using first‐principles calculations. It was found that at Γ point, the conduction band splits into two bands upon inclusion of spin‐orbit coupling (SOC) interaction for X2TeY6 compound. Besides, the highest occupied molecular orbital is unchanged for all studied compounds except that of X2TeI6, which is shifted from W to X point. Our findings appear to be well supported by the experimental data (Annalise E. Maughan et al., J Am Chem Soc. 2016;138:8453‐8464). This shows a contradiction with the theoretical work found by Malak Azmat Ali et al., Int. J. Energy Res. 2020;45:8448‐8455. Hence, the inclusion of SOC is crucial for the correct characterization of the electronic properties of the X2TeY6 compound. Otherwise, the absorption coefficients shift to the visible region by the substitution of Cl by Br and I ions. Thus, the excellent absorption coefficients percentages of Cs2TeI6 (62%‐75%) and Rb2TeI6 (57%‐76%) along the visible region, their suitable forbidden bands (1.422 eV for Cs2TeI6, and 1.469 eV for Rb2TeI6) and their high stabilities make both Cs2TeI6 and Rb2TeI6 as new potential candidates' compounds for single‐junction solar cells. [ABSTRACT FROM AUTHOR]

The effects of the vacancy concentration at the cation site of three half-Heuslers, VCoSb, NbCoSb, and TaCoSb, were studied with a combination of two computational methods: density functional theory and Monte Carlo simulations, both linked by a cluster expansion method. Our density functional method allows us to follow a gap opening in the electronic density of states in NbCoSb and TaCoSb as a function of vacancy concentration, starting from a metallic state with the Fermi-level crossing the valence states in the pristine crystal, passing throughout a p-type doped behavior, down to a semiconducting state at 20% of vacancies. In the case of VCoSb, the transition starts from the half-metallic ferromagnetic state, where VCoSb remains half-metallic until it achieves a semiconductor state at V 0.8 CoSb composition, the transition leading to a magnetic–nonmagnetic crossover. Further increase of vacancies leads to non-polarized in-gap states in V 0.75 CoSb, and polarized in-gaps in Nb 0.77 CoSb, while Ta 0.75 CoSb recovers a metallic behavior but with an n-character. Based on our cluster expansion, we can assert that Ta 0.8 CoSb is slightly more stable than Nb 0.8 CoSb, while both are much more stable than V 0.8 CoSb. Temperature effects were studied through Monte Carlo simulations. The simulations show that, upon cooling, the ground states are hard to recover, and instead metastable states are formed. The vacancy arrangements were scrutinized with the help of suitable order parameters for the lattice vacancy occupation. [ABSTRACT FROM AUTHOR]