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We report the results of an ab initio study of the electronic, optical and thermodynamic properties of the LiBaP and LiSrP compounds using the pseudopotential plane-wave method within the framework of the density functional theory with the GGA-PBEsol. The calculated equilibrium structural parameters are in good agreement with the available experimental data. The energy band dispersions along the high symmetry directions in the k-space and the density of states diagrams are computed and analyzed. The obtained energy bands show that both examined crystals are indirect band gap semiconductors. The chemical bonding character is examined via electron density map plots. The optical properties are predicted for an incident radiation in an energy range up to 15 eV, and the origins of the main peaks in the optical spectra are discussed in terms of the calculated electronic band structure. We have also predicted the temperature and pressure dependencies of the unit-cell volume, thermal expansion coefficient, heat capacity, Debye temperature and Grüneisen parameter. [ABSTRACT FROM AUTHOR]

We report a systematic study of the structural, electronic, optical and elastic properties of the ternary ruthenium-based hydridesA2RuH6(A = Mg, Ca, Sr and Ba) within two complementary first-principles approaches. We describe the properties of theA2RuH6systems looking for trends on different properties as a function of theAsublattice. Our results are in agreement with experimental ones when the latter are available. In particular, our theoretical lattice parameters obtained using the GGA-PBEsol to include the exchange-correlation functional are in good agreement with experiment. Analysis of the calculated electronic band structure diagrams suggests that these hydrides are wide nearly direct band semiconductors, with a very slight deviation from the ideal direct-band gap behaviour and they are expected to have a poor hole-type electrical conductivity. The TB-mBJ potential has been used to correct the deficiency of the standard GGA for predicting the optoelectronic properties. The calculated TB-mBJ fundamental band gaps are about 3.53, 3.11, 2.99 and 2.68 eV for Mg2RuH6, Ca2RuH6, Sr2RuH6and Ba2RuH6, respectively. Calculated density of states spectra demonstrates that the topmost valence bands consist ofdorbitals of the Ru atoms, classifying these materials asd-type hydrides. Analysis of charge density maps tells that these systems can be classified as mixed ionic-covalent bonding materials. Optical spectra in a wide energy range from 0 to 30 eV have been provided and the origin of the observed peaks and structures has been assigned. Optical spectra in the visible range of solar spectrum suggest these hydrides for use as antireflection coatings. The single-crystal and polycrystalline elastic moduli and their related properties have been numerically estimated and analysed for the first time. [ABSTRACT FROM AUTHOR]

The electronic, thermoelectric, optical, and magnetic properties of the samarium aluminate (SmAlO3) compound is studied using the spin-polarized full-potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). The exchange and correlation potential is treated with the generalized gradient approximation (GGA) and the Coulomb repulsion ( Ry) has been calculated theoretically and was used for the GGA based approximated electronic structures. Additionally, the modified Becke-Johnson (mBJ) potential was also utilized along with the GGA approach for the calculation of the band gap. On the other hand, the optical properties were analyzed with the mBJ results and the thermoelectric properties were explained on the basis of the electronic structures and density of states (DOS) with a thermoelectric efficiency of 0.66 at 300 K. The minimum reflectivity at 1.13 eV (which was equal to 1.097 m) was found to be in agreement with the experimental results. Further refinements in the electronic structures were obtained by adding the spin-orbit coupling (SOC) interactions to the GGA approach, which was then combined with the mBJ approximations. Hence, a conclusion using the combined mBJSOC study indicates that the SmAlO3 compound is a potential candidate for both thermoelectric as well as magnetic devices. [ABSTRACT FROM AUTHOR]

The structural, electronic and optical properties of (BeTe)n/(ZnSe)m superlattices have been computationally evaluated for different configurations with m = n and m ≠ n using the full-potential linear muffin-tin method. The exchange and correlation potentials are treated by the local density approximation (LDA). The ground state properties of (BeTe)n/(ZnSe)m binary compounds are determined and compared with the available data. It is found that the superlattice band gaps vary depending on the layers used. The optical constants, including the dielectric function ɛ(ω), the refractive index n(ω) and the refractivity R(ω), are calculated for radiation energies up to 35 eV. [ABSTRACT FROM AUTHOR]

We investigated the structural stability as well as the mechanical, electronic and magnetic properties of the Full-Heusler alloy CoNiMnSi using the full-potential linearized augmented plane wave (FP-LAPW) method. Two generalized gradient approximations (GGA and GGA + U) were used to treat the exchange-correlation energy functional. The ground state properties of CoNiMnSi including the lattice parameter and bulk modulus were calculated. The elastic constants (Cij) and their related elastic moduli as well as the thermodynamic properties for CoNiMnSi have been calculated for the first time. The existence of half-metallic ferromagnetism (HM-FM) in this material is apparent from its band structure. Our results classify CoNiMnSi as a new HM-FM material with high spin polarization suitable for spintronic applications. [ABSTRACT FROM AUTHOR]

The structural parameters, elastic constants, electronic structure and optical properties of the recently reported monoclinic quaternary nitridoaluminate LiCaAlN2are investigated in detail using theab initioplane-wave pseudopotential method within the generalized gradient approximation. The calculated equilibrium structural parameters are in excellent agreement with the experimental data, which validate the reliability of the applied theoretical method. The chemical and structural stabilities of LiCaAlN2are confirmed by calculating the cohesion energy and enthalpy of formation. Chemical band stiffness is calculated to explain the pressure dependence of the lattice parameters. Through the band structure calculation, LiCaAlN2is predicted to be an indirect band gap of 2.725 eV. The charge-carrier effective masses are estimated from the band structure dispersions. The frequency-dependent dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity coefficient and electron energy loss function spectra are calculated for polarized incident light in a wide energy range. Optical spectra exhibit a noticeable anisotropy. Single-crystal and polycrystalline elastic constants and related properties, including isotropic sound velocities and Debye temperatures, are numerically estimated. The calculated elastic constants and elastic compliances are used to analyse and visualize the elastic anisotropy of LiCaAlN2. The calculated elastic constants demonstrate the mechanical stability and brittle behaviour of the considered material. [ABSTRACT FROM AUTHOR]

We performed ab initio calculations using the FPLAW method with the local density approximation (LDA) implemented in the WIEN2 k code for the orthorhombic (α) and triclinic (β) phases of BiNbO. The modified Becke-Johnson exchange potential (mBJ)-LDA approach was also used to improve the electronic properties. The lattice constants calculated for both structures using the LDA are in good agreement with the experimental values. For the band structure calculations, the mBJ-LDA approach provides reasonable agreement for the band gap value compared with the LDA. The estimated (mBJ)-LDA band gap values are 2.89 eV (3.73 eV) and 2.62 eV (3.15 eV) for the α and β phases of BiNbO, respectively. Significant optical anisotropy is clearly observed in the visible-light region. We also calculated and evaluated the electron energy loss spectrum for BiNbO. This work provides the first quantitative theoretical prediction of optical properties and electron energy loss spectra for both the orthorhombic and triclinic phases of BiNbO. [ABSTRACT FROM AUTHOR]

We present the magnetic and optical properties of various combinations of ordered spin state configurations between low-spin (LS) state, intermediate-spin (IS) state, and high-spin (HS) state of LaCoO3. In this study, we use the state-of-the-art first principles calculations based on generalized gradient (GGA) + Hubbard U approach. The excited-state properties of different spin configurations of LaCoO3 such as the X-ray absorption spectra, optical conductivity, reflectivity, and electron energy loss are calculated. We have demonstrated that the optical spectra results can be used for analyzing the spin state of Co3+ ion. The first specie is the local excitation of IS cobalt ions in the LS ground state. The second excitation leads to the stabilization of the mixed IS/HS Co3+ metallic state. At low temperature, the comparison between O 2p and Co 3d projected density of states with the experimental valence band spectra indicates significant IS Co3+ ions and this is in sharp contrast to the HS state which is negligible. The line shape of O 2s and Co 3d core level spectra are well reproduced in this study. The present results are in excellent agreement with the available experimental data. The variation in the spectra of different configurations of LaCoO3 suggests a changing in the spin state as the temperature is enhanced from 90 to 500 K. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2012 [ABSTRACT FROM AUTHOR]

The elastic, electronic and thermodynamic properties of fluoro-perovskite KZnF have been calculated using the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated with the generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE). Also, we have used the Engel and Vosko GGA formalism (GGA-EV) to improve the electronic band structure calculations. The calculated structural properties are in good agreement with available experimental and theoretical data. The elastic constants C are calculated using the total energy variation with strain technique. The shear modulus, Young's modulus, Poisson's ratio and the Lamé coefficients for polycrystalline KZnF aggregates are estimated in the framework of the Voigt-Reuss-Hill approximations. The ductility behavior of this compound is interpreted via the calculated elastic constants C. Electronic and bonding properties are discussed from the calculations of band structure, density of states and electron charge density. The thermodynamic properties are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of bulk modulus, lattice constant, heat capacities and the Debye temperature with pressure and temperature are successfully obtained. [ABSTRACT FROM AUTHOR]

Structural parameters, electronic structure and optical properties of the dialkali metal monotelluride M 2 Te (M = Li, Na, K and Rb) compounds in the cubic antifluorite structure were investigated via ab initio calculations using the all electron linearized augmented plane wave approach based on density functional theory with and without including spin-orbit coupling (SOC). The exchange-correlation interactions were described within the PBEsol version of the generalized gradient approximation and Tran-Blaha modified Becke–Johnson potential (TB-mBJ). Optimized equilibrium lattice parameters are in excellent accordance with existing measured ones. Computed energy band dispersions show that the studied compounds are large band gap materials. Inclusion of SOC reduces the band gap value compared to the corresponding one calculated without including SOC. Determination of the energy band character and interatomic bonding nature are performed using the densities of states diagrams and charge density distribution map. Linear optical function spectra are predicted for a wide energy range and the origin of the dielectric function spectrum peaks are determined. Image 1 • Structural, electronic and optical properties of the M 2 Te materials have been predicted. • The M 2 Te [M: Li, Na, K, Rb] systems are found to be wide gap materials. • These materials are characterized by an ionic intra-atomic chemical bonding. • M 2 Te materials exhibit a noticeable optical absorption in the ultraviolet range. [ABSTRACT FROM AUTHOR]

In this paper, the structural, mechanical, electronic, and thermodynamic properties of Ir 3 TM (TM = Sc, Ti, and V) intermetallic compounds in the cubic (L1 2) and hexagonal (D0 19 and D0 24) phases are presented. The outcomes of the simulation rely on density functional theory (DFT) within the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) based on the full-potential linearized augmented plane wave (FP-LAPW) approach. The existing study was performed on the L1 2 cubic phase. in addition to hexagonal D0 24 and D0 19 phases, which may be relative but differ in the way that the atomic layers are stacked. The calculated total, cohesive energy, and heat formation suggest that the Ir 3 Sc compound can be stable in the D0 24 phase because of an overlap between the L1 2 and D0 24 phases with a total energy difference of around 0.026 eV/atom. Ir 3 Ti and Ir 3 V are more stable in L1 2 and D0 19 , respectively. From elastic constants calculations, it reveals that the studied compounds are mechanically stable and harder in the cubic phase than hexagonal phase. However, Ir 3 Sc has the lowest hardness due to its relative ductility. Inversely, Ir 3 V has the maximum hardness with a lack of ductility. It was observed that these compounds have an elastic anisotropy based on the three-dimensional Young's modulus surface, and Ir 3 Sc has the strongest anisotropy, while Ir 3 V has the weakest in the L1 2 phase. The total density of state (TDOS) calculations shows that Ir 3 Ti and Ir 3 V are stable in the L1 2 and D0 19 phases, respectively, except for the Ir3Sc compound which might undergo a martensitic transition. Also, the pseudogap for Ir 3 V moves quite close to the Fermi level, indicating that the covalent bonding in this compound is sharper than the other compounds. Moreover, via the quasi-harmonic Debye model within the Gibbs computational code, thermodynamic properties are calculated and analyzed with temperature and pressure. [ABSTRACT FROM AUTHOR]

First-principles density functional theory calculations were performed to predict some of the not yet explored physical properties of the monoclinic quaternary nitridogallate LiCaGaN 2 . The calculated lattice parameters, including the lattice constants, angle β and internal atomic coordinates, are in excellent agreement with the corresponding measured ones, proving the reliability of the chosen theoretical approach. The equation of state, pressure dependence of the lattice constants, unit cell volume, angle β and bond-lengths were explored in detail. The single-crystal and polycrystalline elastic constants and their pressure dependence were numerically estimated. The mechanical stability, ductility/brittleness, average elastic wave velocity, Debye temperature and elastic anisotropy were also assessed. The electronic structure and its evolution with external applied hydrostatic pressure were explored. The bonding character was demonstrated by calculating the site-projected density of states, charge density and effective Mulliken charges of all ions. The effective masses of the charge-carriers were numerically estimated. The complex dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity and electron energy-loss function spectra were calculated for different polarizations of the incident light. Pressure dependence of the static dielectric constant, static refractive index and static reflectivity are also reported. To the best of our knowledge, this is the first attempt to explore the aforementioned physical properties for the title material. [ABSTRACT FROM AUTHOR]

Abstract: The structural, electronic and optical properties of the cubic spinels SnB2O4, with B=Mg, Zn and Cd, were studied by means of the full-potential (linear) augmented plane wave plus local orbitals method within the local density and generalized gradient approximations for the exchange-correlation potential. The Engel–Vosko form of the generalized gradient approximation (EV-GGA), which better optimizes the potential for the band structures, was also used. The results of bulk properties, including lattice constants, internal parameters, bulk moduli and their pressure derivatives are in good agreement with the literature data. The band structures show a direct band gap (Γ–Γ) for the three compounds. The computed band gaps using the EV-GGA show a significant improvement over the more common GGA. All the calculated band gaps increase with increasing pressure and fit well to a quadratic function. Analysis of the density of states revealed that the lowering of the direct gap (Γ–Γ) from SnMg2O4 to SnZn2O4 to SnCd2O4 can be attributed to the p–d mixing in the upper valence band of SnZn2O4 and SnCd2O4. We present calculations of the frequency-dependent complex dielectric function ɛ(ω). We find that the values of zero-frequency limit ɛ 1(0) increase with decreasing the energy band gap. The origin of the peaks and structures in the optical spectra is determined in terms of the calculated energy band structures. [Copyright &y& Elsevier]

Abstract Density functional FP-LAPW+lo method calculations were performed to explore the structural, electronic, optical, elastic, thermoelectric and thermodynamic properties of the spinel oxides ZnRh 2 O 4 and CdRh 2 O 4. The exchange-correlation potential were described using the GGA-PBEsol and TB-mBJ functionals. As the first step, the optimized structural parameters, including the lattice parameter and atomic coordinates, were determined. Electronic band structure, atomic-resolved l -projected densities of electronic states and photon energy dependence of the linear optical functions were computed. It is found that both investigated compounds are indirect band gap semiconductors. The band gap results from the splitting of the R h : 4 d 6 states into occupied R h : 4 d − t 2 g 6 states, which form the valence band maximum (VBM), and the empty states R h : 4 d − e g 0 , which form the conduction band minimum (CBM), owing to the octahedral substantial crystal-field. The electronic interband transitions responsible of the structures in the optical spectra were specified. Single-crystal and polycrystal elastic moduli, wave sound velocities, Debye temperature, Pugh's indicator and indexes of elastic anisotropy were numerically estimated using total energy versus strain. FP-LAPW+lo band structure in combination with the standard Boltzmann transport theory were employed to calculate the thermoelectric parameters, including Seebeck coefficient, electrical and thermal conductivities and figure of merit. It is found that the title compounds are potential candidates for thermoelectric applications if one can further reduce their thermal conductivities via some techniques. FP-LAPW+lo approach in combination with the quasi-harmonic Debye model was employed to study temperature and pressure dependences of some macroscopic physical parameters. Our obtained results in the present work are discussed in comparison with the available experimental and theoretical data. The calculated results show a good agreement with the available experimental and theoretical results. Highlights • Optoelectronic and thermoelectric properties of the Zn/CdRh 2 O 4 spinels have been predicted. • Zn/CdRh 2 O 4 systems are quasi-direct band gap semiconductors. • n -type doped compounds are more favourable for electrical conductivity performance than the n -type doped ones. • p -type doped compounds are more favourable for thermoelectric performance than the n -type doped ones. [ABSTRACT FROM AUTHOR]

Strontium-based Zintl materials SrCd 2 Pn 2 (Pn = P/As) have been investigated here for their thermoelectric applications. The fundamental structural, optoelectronics and transport properties of Zintl SrCd 2 Pn 2 (Pn = P/As) compounds were determined by employing the full potential linearized augmented plane wave approach (FP-LAPW). The formation and dynamical stabilities have been confirmed by formation energy and phonon dispersion studies. The established band structures using the modified Becke–Johnson potential (mBJ) reveals a direct energy bandgap (E g) of 1.58 eV and 1.15 eV for SrCd 2 P 2 and SrCd 2 As 2 , respectively. The DOS spectra disclose Pn(P/As) states are present in the valence band while Sr states are present in the conduction band. The optical features of the compounds were analyzed from dielectric constants, refractive index, extinction coefficient, and energy loss function against photon energy (eV) up to 30 eV. We observed that the material absorption by falling the light is fascinating in the visible region, revealing a viable choice for optoelectronics application. We evaluated transport properties like the Seebeck coefficient, electrical and thermal conductivity, power factor versus temperature, carrier concentration, and chemical potential with the classical Boltzmann transport theory. The computed Seebeck coefficients for SrCd 2 P 2 and SrCd 2 As 2 are found to be equal to 242μVK−1 and 239 μVK−1 at 300 K and 255 μVK−1, 257 μVK−1at 1200 K. The highest values of the power factor obtained at 1200 K are 5.88 × 1011 W/K2m.s, 5.21 × 1011W/K2m.s for SrCd 2 P 2 and SrCd 2 As 2 , respectively. The tremendous optoelectronic characteristic and outstanding power factor values predicted this group could be favorable for uses in solar and thermoelectric uses. The structural properties of SrCd2 2Pn (Pn=P/As) compounds were examined, and it was established that they have a trigonal crystal structure (P-3m1). Phonon investigations provide information about their dynamical stability. The SrCd2 2 Y 2 (Y P/As) compounds under investigation have a high figure of merit (ZT), which suggests their usage in thermoelectric devices. [Display omitted] • Some physical properties of Zintl compounds SrCd2 2Pn (Pn=P/As) are investigated. • The SrCd 2 P 2 and SrCd 2 As 2 compounds are direct band gap semiconductors. • The vibrational properties reveal the dynamical stability of the compounds. • The large power factor for both compounds suggest that they are potential candidates for thermoelectric applications. [ABSTRACT FROM AUTHOR]

By using the full potential linearized augmented plane wave (FP-LAPW) method, the electronic properties of the layered BaAg Ch F ( Ch  = S, Se, Te) were investigated. Both the standard GGA and the TB-mBJ potential were used to model the exchange-correlation potential. To evaluate the spin-orbit coupling (SOC) effect, both the scalar relativistic and full relativistic calculations were performed. The SOC effect is found to be not negligible in the title compounds. The FP-LAPW band structure and the semi-classical Boltzmann transport theory were used to study the charge-carrier concentration and temperature dependences of the thermoelectric parameters, including Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit. Our results show that the values of the thermoelectric parameters of the p -type compounds are larger than that of the n -type ones. The optimal p -type doping concentrations and temperatures that yield the maximum values of the figure of merit of the title compounds were calculated. These are important parameters to guide experimental works. [ABSTRACT FROM AUTHOR]

The structural, elastic, electronic and optical properties of two newly synthetized quaternary diamond-like semiconductors Cu 2 MgSiS 4 and Cu 2 MgGeS 4 were studied in detail using two complementary first-principles approaches. The calculated equilibrium structural parameters are in good agreement with the available experimental data. Single-crystal and polycrystalline elastic moduli and their related properties, including elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy indexes, Pugh's criterion, elastic wave velocities and Debye temperature, were predicted. We find that the inclusion of the electronic exchange-correlation through the newly developed Tran-Blaha modified Becke–Johnson potential (TB-mBJ) improves the description of the electronic structure. The TB-mBJ yields a direct band gap (Γ-Γ) of 2.64 and 1.54 eV for Cu 2 MgSiS 4 and Cu 2 MgGeS 4 , respectively. Frequency dependence of the dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity, energy loss function and optical conductivity were predicted and the origin of the observed electronic transitions were assigned. [ABSTRACT FROM AUTHOR]

The structural, electronic and optical properties of the cubic RbMF 3 perovskites (M = Be, Mg, Ca, Sr, Ba) have been investigated using the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange and correlation potential was applied using the generalized gradient approximation for calculating the structural properties In addition, the modified Becke-Johnson (TB-mBJ) potential was used for calculating the electronic and optical properties. It was found that the lattice constant increases while the bulk modulus decreases with the change of cation (M) in going from Be to Ba in the RbMF 3 perovskites (M = Be, Mg, Ca, Sr, Ba). The reflectivity and absorption properties were also studied using the mBJ method to understand the inter-band transitions and their possible applications in absorption devices in the UV-region. [ABSTRACT FROM AUTHOR]

Ab initio calculations based on density functional theory were performed to determine the structural parameters of the Lu X Co 2 Sb 2 (X = V, Nb and Ta) double half Heusler compounds and verify their thermodynamic stability in an orthorhombic structure as well as to predict their electronic and optical properties. The predicted electronic band structures show that LuVCo 2 Sb 2 , LuNbCo 2 Sb 2 , and LuTaCo 2 Sb 2 are semiconductors with indirect bandgaps of 0.728, 0.845, and 0.898 eV, respectively. The effective masses calculated at the valence band maximum at the conduction band minimum show a strong anisotropy. It can be seen that electrons are lighter than holes. The nature of the electronic states involved in the formation of the energy bands has been determined thanks to the density of states calculations. The character of chemical bonds was analyzed through the charge density distribution map. Linear optical functions, namely complex dielectric function, absorption coefficient, optical reflectivity and refractive index, were calculated for all compounds in an energy range up to 20 eV. The calculated optical spectra exhibit a noticeable anisotropy. The compounds under consideration are characterized by strong absorption of incident electromagnetic radiation in a wide energy range. [ABSTRACT FROM AUTHOR]

Using the first-principles density functional calculations, the structural, electronic and magnetic properties of the Fe 2 XAl (X=Cr, Mn, Ni) compounds in both the Hg 2 CuTi and Cu 2 MnAl-type structures were studied by the full-potential linearized augmented plane waves (FP-LAPW) method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA) where the results show that the Cu 2 MnAl-type structure is energetically more stable than the Hg 2 CuTi-type structure for the Fe 2 CrAl and Fe 2 MnAl compounds at the equilibrium volume. The full Heusler compounds Fe 2 XAl (X=Cr, Mn) are half-metallic in the Cu 2 MnAl-type structure. Fe 2 NiAl has a metallic character in both CuHg 2 Ti and AlCu 2 Mn-type structures. The total magnetic moments of the Fe 2 CrAl and Fe 2 MnAl compounds are 1.0 and 2.0 μ B , respectively, which are in agreement with the Slater–Pauling rule M tot =Z tot − 24. [ABSTRACT FROM AUTHOR]

Different exchange correlation potential approximations are used to examine electronic, optical, and thermoelectric properties of X NMg 3 ( X =P, As, Sb, and Bi) antiperovskite compounds. Band structures of the compounds are direct in nature. Within a high-energy range (2–6 eV), these materials exhibit maximum levels of optical conductivity, and these materials may therefore be used in radiation detectors and solar cells. Optical properties such as dielectric function, optical conductivity, reflectivity, refractive indices and absorption coefficients vary in transitions from P to Bi. Furthermore, calculated peaks of conductivity and absorption coefficient values decrease with increasing photon energy. With respect to thermoelectric properties, electrical conductivity, Seebeck coefficient and thermal conductivity levels vary with increase in temperature, thus resulting in the formation of thermoelectric materials. [ABSTRACT FROM AUTHOR]

The structural, electronic and magnetic properties of half-Heusler CoFeIn and full-Heusler Co 2 FeIn alloys have been investigated by using the state of the art full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential was treated with the generalized gradient approximation (PBE-GGA) for the calculation of the structural properties, whereas the PBE-GGA+ U approximation (where U is the Hubbard Coulomb energy term) is applied for the computation of the electronic and magnetic properties in order to treat the “ d ” electrons. The structural properties have been calculated in the paramagnetic and ferromagnetic phases where we have found that both the CoFeIn and Co 2 FeIn alloys have a stable ferromagnetic phase. The obtained results of the spin-polarized band structure and the density of states show that the CoFeIn alloy is a metal and the Co 2 FeIn alloy has a complete half-metallic nature. Through the obtained values of the total spin magnetic moment, we conclude that in general, the Co 2 FeIn alloy is half-metallic ferromagnet material whereas the CoFeIn alloy has a metallic nature. [ABSTRACT FROM AUTHOR]

The structural, mechanical, electronic and magnetic properties of the series of Heusler alloys CoFeMnZ (Z=Si, As, and Sb) have been investigated theoretically. The objective is to seek for stable half-metallic ferromagnets materials with Curie temperatures higher than room temperature. The series of CoFeMnZ (Z=Si, As and Sb) is found to exhibit half-metallic ferromagnetism with high magnetic moment and the localized moment in these magnetic compounds resides at the Mn atom. It has been observed that all our compounds have high Curie temperatures with high spin polarizations. [ABSTRACT FROM AUTHOR]

First-principle calculations are performed to predict the electronic structure and elastic and magnetic properties of CoRhMnZ (Z = Al, Ga, Ge and Si) Heusler alloys. The calculations employ the full-potential linearized augmented plane wave. The exchange-correlations are treated within the generalized gradient approximation of Perdew–Burke and Ernzerhof (GGA-PBE). The electronic structure calculations show that these compounds exhibit a gap in the minority states band and are clearly half-metallic ferromagnets, with the exception of the CoRhMnAl and CoRhMnGa, which are simple ferromagnets that are nearly half metallic in nature. The CoRhMnGe and CoRhMnSi compounds and their magnetic moments are in reasonable agreement with the Slater-Pauling rule, which indicates the half metallicity and high spin polarization for these compounds. At the pressure transitions, these compounds undergo a structural phase transition from the Y-type I → Y-type II phase. We have determined the elastic constants C 11 , C 12 and C 44 and their pressure dependence, which have not previously been established experimentally or theoretically. [ABSTRACT FROM AUTHOR]

In this study, the structural, magnetic, electronic, elastic and thermal properties of the ternary intermetallic, RMn 2 Si 2 (R=Ce and Nd), compounds are presented. The study is carried out by employing the full-potential (FP) linearized augmented plane wave (LAPW) plus local orbital (lo) approach based on the density functional theory (DFT). To depict the exchange-correlation energy (an important component of total energy calculations), the local-density approximation and the local spin density approximation (LDA/LSDA) are used. Our calculated results for equilibrium lattice parameters are in good agreement with the available experimental measurements. The total energy calculations reveal the strong dependence to the distance between atomic species in these compounds. The analysis of the partial and total densities of states (DOS) of both compounds (CeMn 2 Si 2 and NdMn 2 Si 2 ) demonstrates their metallic and magnetic character as well. Whereas the calculated values of Poisson׳s ratio and B / G present their brittle makeup. At the end, using a quasi-harmonic Debye model as implemented in GIBBS code, the thermal properties were calculated. [ABSTRACT FROM AUTHOR]

First-principles calculations in the framework of density functional theory have been conducted to explore the structural, elastic, electronic and optical properties of two layered ternary compounds chalcogenides of aluminum KAlSe 2 and KAlTe 2 . We have calculated all of the equilibrium structural parameters; the lattice parameters ( a , b and c ), angle β and twenty three internal atomic coordinates. The obtained results are in excellent agreement with the available experimental data. We have predicted the single-crystal elastic constants C ij of the title materials using stress-strain approach and then derived the elastic moduli of the polycrystalline aggregates and related properties via the Voigt-Reuss-Hill approximations. The band structure and density of states diagrams have been calculated and analyzed. Both compounds demonstrate semiconducting behavior with direct band gap. The linear optical properties, namely the frequency-dependent dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and energy-loss function, have been calculated and analyzed in a wide energy range up to 20 eV. [ABSTRACT FROM AUTHOR]

The state-of-the-art all-electron FLPAW method and the BoltzTrap software package based on semi-classical theory were adopted to explore the electronic structure and the optical and thermoelectric properties of Ga 1−x In x N. Ga 1−x In x N is predicted to be a direct band gap material for all values of x . Moreover, the band gap varies between 2.99 eV and 1.95 eV as x changes. Optical parameters such as the dielectric constant, absorption coefficient, reflectivity and refractive index are calculated and discussed in detail. The doping of In plays an important role in the modulation of the optical constants. The static dielectric constant ɛ (0) of Ga 1−x In x N was calculated as 3.95, 3.99, 3.99 and 4.03 at x = 0.00, 0.25, 0.50 and 0.75, respectively. The static refractive index is 2.0 for pure Ga 1−x In x N at x = 0.00. The thermal properties varied greatly as x fluctuated. The ternary alloy has large values for the Seebeck coefficient and figure of merit at high temperatures and is thus suitable for thermoelectric applications. Pure Ga 1−x In x N at x = 0 exhibited ZT = 0.80 at room temperature, and at higher temperatures, the thermal conductivity decreased with increased In doping. [ABSTRACT FROM AUTHOR]

The PLANE WAVE pseudo-potential method within density functional theory (DFT) has been used to investigate the structural, elastic, electronic and optical properties of XCaF 3 (X = K and Rb) insulating. The studied compounds show a weak resistance to shear deformation compared to the resistance to the unidirectional compression. KCaF 3 and RbCaF 3 are considered ductile. The elastic constants and related parameters were predicted. The stiffness is more important in KCaF 3 , whereas, the lateral expansion is more important in RbCaF 3 . KCaF 3 and RbCaF 3 have R- Г indirect band gap. The main peaks in the imaginary part of the dielectric function correspond to the transition from the occupied state F − p to the unoccupied states Ca: s or K, Rb: p. At lower energies, KCaF 3 and RbCaF 3 show the same optical properties. Under pressure effect, the peaks of imaginary part of dielectric function were shifted toward high energy. [ABSTRACT FROM AUTHOR]

First-principles calculations have been used to study the structural, elastic, electronic, magnetic and thermal properties of zinc blende Zn 1− x V x Te for x =0, 0.25, 0.50, 0.75 and 1 using the full-potential linearized augmented plane wave method (FP-LAPW) based on spin-polarized density functional theory (DFT). The electronic exchange-correlation potential is approached using the spin generalized gradient approximation (spin-GGA). The structural properties of the Zn 1− x V x Te alloys ( x =0, 0.25, 0.50, 0.75 and 1) are given for the lattice constants and the bulk moduli and their pressure derivatives. The elastic constants C 11 , C 12 and C 44 are calculated using numerical first-principles calculations implemented in the WIEN2k package. An analysis of the band structures and the densities of states reveals that Zn 0.50 V 0.50 Te and Zn 0.75 V 0.25 Te exhibit a half-metallic character, while Zn 0.25 V 0.75 Te is nearly half-metallic. The band structure calculations are used to estimate the spin-polarized splitting energies Δ x ( d ) and Δ x ( pd ) produced by the V(3 d )-doped and s ( p ) –d exchange constants N 0 α (conduction band) and N 0 β (valence band). The p–d hybridization reduces the magnetic moment of V from its atomic charge value of 3 µ B and creates small local magnetic moments on the nonmagnetic Zn and Te sites. Finally, we present the thermal effect on the macroscopic properties of these alloys, such as the thermal expansion coefficient, heat capacity and Debye temperature, based on the quasi-harmonic Debye model. [ABSTRACT FROM AUTHOR]

First-principles calculations using the full potential linearized augmented plane wave method within the framework of density functional theory are performed to investigate the compositional dependence of the structural, electronic and optical properties of Zn 1− x Hg x E (E=S, Se, Te). It is observed that except the lattice constant, the variation of the bulk modulus and the band gap versus mercury composition does not obey Vegard׳s law. The alloys at all concentrations have direct band gap ( Γ − Γ ) which decreases with increasing the concentration of Hg. Optical properties like complex dielectric function and reflectivity are discussed comprehensively. The properties of these materials such as the direct band gap and high absorption in the infrared to ultraviolet regions demonstrate the significant optical activity of these materials. [ABSTRACT FROM AUTHOR]

Structural parameters, elastic constants, thermodynamic properties, electronic structure and optical properties of the monoclinic Li 4 Sr 3 Ge 2 N 6 quaternary nitride are investigated theoretically for the first time using the pseudopotential plane-wave based first-principles calculations. The calculated structural parameters are in excellent agreement with the experimental data. This serves as a proof of reliability of the used theoretical method and gives confidence in the predicted results on aforementioned properties of Li 4 Sr 3 Ge 2 N 6 . The predicted elastic constants C ij reveal that Li 4 Sr 3 Ge 2 N 6 is mechanically stable but anisotropic. The elastic anisotropy is further illustrated by the direction-dependent of the linear compressibility and Young’s modulus. Macroscopic elastic parameters, including the bulk and shear moduli, the Young’s modulus, the Poisson ratio, the velocities of elastic waves and the Debye temperature are numerically estimated. The pressure and temperature dependence of the unit cell volume, isothermal bulk modulus, volume expansion coefficient, specific heat and Debye temperature are investigated through the quasiharmonic Debye model. The band structure and the density of states of Li 4 Sr 3 Ge 2 N 6 are analyzed, which reveals the semiconducting character of Li 4 Sr 3 Ge 2 N 6 . The complex dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity and electron energy-loss function are calculation for incident radiation polarized along the crystallographic directions and for energy up to 40 eV. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lattice constants vary inversely to the bulk moduli in these alloys. [•] Structural parameters vary non-linearly by doping concentration. [•] Binaries have indirect band gap while their ternary alloys show direct band gap. [•] The band gaps also varies non-linearly with the concentration. [•] The alloys can be utilized in solar cells and other optoelectronic devices. [Copyright &y& Elsevier]

Highlights: [•] KMF3 (M=Mn, Fe, Co, Ni) compounds exist in cubic structure. [•] The compounds are stable elastically. [•] KFeF3 and KCoF3 are half metallic. [•] Compounds show mixed ionic and covalent bonding. [•] Compounds show ferromagnetic behavior. [ABSTRACT FROM AUTHOR]

Over the years, vanadates are attracting sizable consideration of the researchers owing to their versatile functional properties. Through an ab initio computational approach, a comprehensive study was performed on terbium orthovanadate (TbVO 4); the study includes an investigation on its electronic structure, magnetic behavior, as well as mechanical and optical properties. The computations are performed by employing the "full-potential linearized augmented plane wave plus local orbital (FP-LAPW ​+ ​lo)" methodology framed with "density functional theory (DFT)". To incorporate the "exchange correlation energy/potential" functional into total energy calculations, the "Perdew-Burke and Ernzerhof" approach to "generalized gradient approximation" was employed by using WIEN2k computational code. In addition, to analyze the d-orbital electrons of vanadium (V) and the f-orbital electrons of terbium (Tb) more precisely, the GGA ​+ ​U approximation is also used. The computational obtained results of structural parameters are found to be in good agreement with the experimentally measured one. Moreover, TbVO 4 showed mechanical stability and ductility as well. The computed electronic structure reveals that TbVO 4 is a direct gap semiconductor compound with band gap energy comparable to that of the experimentally one. The magnetic moment and density of states results confirm that TbVO 4 is an antiferromagnetic material. For completeness, the optical and mechanical anisotropy are also simulated and analyzed. [Display omitted] • Some Physical properties for tetragonal TbVO 4 in its antiferromagnetic state are investigated. • The calculated ground states properties for TbVO 4 compare well with the available data. • The electronic properties calculation reveals that this compound is wide-direct band gap. • The mechanical, optical and magnetic characteristics for TbVO 4 are investigated for the first time. [ABSTRACT FROM AUTHOR]

We report and discuss the results of a detailed first-principles calculations of the structural, elastic, electronic, optical and thermoelectric properties of the new Zintl phase dibarium zinc diphosphide Ba 2 ZnP 2. The calculated structural parameters using the GGA-PBEsol functional are in excellent agreement with the available experimental counterparts. From the monocrystalline elastic constants numerically estimated through the stress-strain technique, a set of related properties, viz., mechanical stability, elastic anisotropy, brittle/ductile character, anisotropic sound velocities, polycrystalline elastic moduli, including isotropic bulk modulus, shear modulus, Young's modulus, Poisson's ratio, average sound velocity and Debye temperature, are deduced. The electronic and optical properties are investigated through the state-of-the art FP-(L)APW + lo method with the accurate TB-mBJ potential. Ba 2 ZnP 2 is an indirect semiconductor with a gap of 1.24 eV. The charge-carrier effective masses are calculated. The valence band maximum is less dispersive than the conduction band minimum. The microscopic origins of the electronic states composing the energy bands are determined via the PDOS diagrams. Topological analysis of the charge density shows that a covalent character is dominantly ruling the Zn–P bond inside the block ZnP 4 , while an ionic bonding is mainly ruling the bond between the cation Ba and the polyanion ZnP 4. Frequency-dependent macroscopic linear optical functions are predicted in a wide energy range 0–30 eV. Within the visible spectra, the calculated magnitude of the absorption coefficient, reflectivity and refractive index are in the ranges ∼ 4 − 35 × 1 0 4 cm − 1 , 29 − 36 % and 3. 18 − 3. 47 , respectively. The semi-classical Boltzmann transport theory within the constant relaxation time approximation is used to study the thermoelectric properties. The title compound has a figure of merit of ∼1.77 at 300 K, which makes it a potential candidate for thermoelectric applications. [Display omitted] • Some fundamental physical properties of the novel Zintl-phase Ba 2 ZnP 2 are explored. • It is mechanically stable with moderate stiffness and a significant elastic anisotropy. • It is an indirect bandgap semiconductors with mixed covalent-ionic bond characters. • It exhibits an import absorption of the electromagnetic radiation in the visible and UV spectra. • It can be classified among the TE materials of performant thermoelectricity candidate for thermoelectric applications. [ABSTRACT FROM AUTHOR]

Abstract: Structural, elastic, electronic and thermodynamic properties of the ternary cubic filled skutterudite CeOs4Sb12 compound were calculated using the full-potential linear muffin-tin orbital implementation of density functional theory. The exchange-correlation potential was treated with the local density approximation. The calculated ground state quantities such as the lattice parameter, atomic position parameters of Sb atoms, bulk modulus and its pressure derivative are compared to the available experimental data. We have computed the elastic moduli and their pressure dependence, which have not been calculated or measured yet. The Debye temperature is estimated from the average sound velocity. From the elastic parameter behavior, it is inferred that this compound is elastically stable and brittle in nature. The electronic band structure calculations revealed metallic behavior for the herein studied compound at zero pressure, but under pressure effect, the metallic character disappears and the compound becomes a narrow indirect band gap semiconductor. Through the quasi-harmonic Debye model, in which phononic effects are considered, the effect of pressure P and temperature T on the lattice constant, bulk modulus, heat capacity, thermal expansion coefficient and Debye temperature are investigated. [Copyright &y& Elsevier]

Abstract: The structural, elastic, electronic and optical properties of the gallium monohydrides BaGaXH (X=Si, Ge, Sn) have been investigated by means of first principles calculations. The low values of the B/G ratio of these compounds correspond to the brittle nature, which is due to the hydrogen presence. The bulk modulus, Young's modulus, shear modulus decrease from Si to Sn for BaGaXH (X=Si, Ge, Sn) in the same column in the periodic table. Also the Debye temperature of these compounds has a relative high value indicating that they possess good thermal conductivity. The mean sound velocities have a progressive decrease from silicon (Si) to tin (Sn). [Copyright &y& Elsevier]

Highlights: [•] Elastic, electronic and optical properties of MIn2P2 materials have been predicted. [•] The Zintl phases MIn2P2 are found to be semiconductors with narrow gap. [•] These materials are mechanically stable at ambient condition. [•] These materials show structural and elastic anisotropy abut an optical isotropy. [ABSTRACT FROM AUTHOR]

Abstract: Structural, electronic and optical properties of the ZnSc2S4 and CdSc2S4 cubic spinels have been investigated by means of the full-potential (linearized) augmented plane wave plus local orbitals based on density functional theory. The exchange-correlation potential is treated by the GGA–PBEsol [J.P. Perdew, A. Ruzsinszky, G.I. Csonka, O.A. Vydrov, G.E. Scuseria, L.A. Constantin, X. Zhou, K. Burke, Phys. Rev. Lett. 100 (2008) 136406] and the recently proposed modified Becke–Johnson potential approximation (mBJ) [F. Tran, P. Blaha, Phys. Rev. Lett. 102 (2009) 226401], which successfully corrects the band-gap problem found with GGA for a wide range of materials. The obtained structural parameters are in good agreement with the available experimental data. This gives support for the predict properties for ZnSc2S4 and CdSc2S4. The band structures reveal that both compounds are semiconductor with a direct gap. The obtained gap values show that mBJ is superior for estimating band gap energy. We have calculated the electron and hole effective masses in different directions. The density of states has been analyzed. Based on our electronic structure obtained using the mBJ method we have calculated various optical properties, including the complex dielectric function ɛ(ω), complex index of refraction n(ω), reflectivity coefficient R(ω), absorption coefficient α(ω) and electron energy-loss function L(ω) as functions of the photon energy. We find that the values of zero-frequency limit ɛ 1(0) increase with decreasing the energy band gap in agreement with the Penn model. The origin of the peaks and structures in the optical spectra is determined in terms of the calculated energy band structures. [Copyright &y& Elsevier]

Abstract: The structural, electronic and mechanical properties of ruthenium oxide (IV) (RuO2) in various space groups have been calculated using full-potential linear muffin-tin orbital method. The exchange and correlation potential is treated by local density approximation. The calculated ground state properties, including, lattice constants, internal parameters, bulk modulus and the pressure derivative of the bulk modulus are in good agreement with the available data. This compound is found to undergo a series of structural phase transitions under high pressure. The sequence of the structural phase transition is: rutile→marcasite→pyrite→fluorite that occurs at around 4.92, 22.9 and 100.6GPa, respectively. The elastic constants C ij for RuO2 in its different structures are calculated using the total energy variation with strain technique. The polycrystalline elastic moduli, namely; shear modulus, Young''s modulus, Poisson''s ratio, sound velocities and Debye temperature were derived from the obtained single-crystal elastic constants. Band structure calculations show that this compound is a narrow band gap semiconductor with a gap of 0.47eV in its fluorite structure. While for rutile, marcasite and pyrite structures, this compound exhibits metallic properties. [Copyright &y& Elsevier]

Abstract: Based on first-principles approach, we present a comparative study of structural, electronic, elastic and thermo-dynamical properties of the series of inverse-perovskites Sc3 AC, with A = Al, Ga, In and Tl. The calculated equilibrium lattice constants are in excellent agreement with the experimental and available theoretical data. The electronic band structures and densities of states profiles show that the studied compounds are conductors. Analysis of atomic site projected local density of states and charge densities reveals that a mixture of covalent–ionic–metallic characterizes the chemical bonding of the considered inverse-perovskites. Pressure dependence up to 40 GPa of the single-crystal and polycrystalline elastic constants has been investigated in details. The computed B/G ratios show that all Sc3 AC compounds are brittle. We have estimated the sound velocities in the principal directions. Through the quasi-harmonic Debye model, in which the phononic effects are taken into account, the temperature and pressure effects on the lattice constant, bulk modulus, heat capacity and Debye temperature are performed. [Copyright &y& Elsevier]

Abstract: Some physical properties of the cubic perovskites CsXF3 (X = Ca, Sr and Hg) have been investigated using pseudopotential plane-wave method based on the density functional theory. The calculated lattice parameters within GGA and LDA agree reasonably with the available experimental data. The elastic constants and their pressure derivatives are predicted using the static finite strain technique. We derived the bulk and shear moduli, Young''s modulus, Poisson''s ratio and Lamé’s constants for ideal polycrystalline aggregates. The analysis of B/G ratio indicates that CsXF3 (X = Ca, Sr and Hg) are ductile materials. The thermal effect on the volume, bulk modulus, heat capacity and Debye temperature was predicted. [Copyright &y& Elsevier]

Abstract: The structural, elastic, thermodynamic, electronic and magnetic properties of ferromagnetic tetragonal PrNi2Si2 and PrNi2Ge2 compounds have been calculated using the full-potential linear muffin-tin orbital (FP-LMTO) method. The exchange–correlation potential is treated within the local spin density approximation of Perdew and Wang (LSDA–PW). Moreover, we have added the Coulomb interaction U to improve the electronic band structure calculations and the magnetic properties. The calculated structural parameters are in good agreement with the experimental data. The elastic constants Cij are predicted using the total energy variation versus strain technique. The polycrystalline elastic moduli, namely; shear modulus, Young’s modulus, Poisson’s ratio, sound velocities and Debye temperature are derived from the obtained single-crystal elastic constants. Ductility behavior of these compounds is interpreted via the calculated elastic constants Cij . Electronic and bonding properties are discussed from the calculations of band structure and density of states. The thermodynamic properties are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of the bulk modulus, lattice constant, heat capacities and Debye temperature with pressure and temperature are successfully obtained. [Copyright &y& Elsevier]

Abstract: Density functional-based method has been used to investigate the systematic trends for structural parameters, elastic stiffness, lattice dynamics and thermal properties of cubic perovskite-type RBRh3 depending on the type of R atoms (R are Sc, Y, La and Lu). The structural parameters, single-crystal elastic constants, directional elastic wave velocities and their pressure dependence are calculated and analyzed in comparison with the available experimental and theoretical data. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young’s modulus, Poisson’s ratio, Lamé’s coefficients, average sound velocity, Debye temperature and thermal conductivity are predicted in the frame work of the Voigt–Reuss–Hill approximation for the polycrystalline RBRh3. The correlation between the mechanical properties and electronic structures has been discussed. Using the density-functional perturbation theory (DFPT), the phonon properties of RBRh3 (R =Sc, Y and La) are investigated for the first time. [Copyright &y& Elsevier]

Abstract: The high-pressure structural (B1–B2) phase transition and the elastic properties of ScS and ScSe are studied using the full-potential augmented plane wave plus local orbitals method (FP-APW + LO) with the generalized-gradient approximation (GGA) exchange-correlation functional. The elastic constants and their pressure dependence are calculated following the total energy variation with strain technique. The stability and the ductility mechanisms for these compounds are discussed via the electronic density of states (DOS) and the elastic constants Cij . The thermodynamic properties of (B1) structure are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of bulk moduli, the thermal expansion coefficient, the heat capacities and the Debye temperature with pressure and temperature are successfully obtained. To our knowledge this is the first quantitative theoretical prediction of the elastic, high pressure and thermal properties for the investigated compounds and still awaits experimental confirmations. [Copyright &y& Elsevier]

Abstract: An accurate ab initio full potential linear muffin-tin orbital method has been used to investigate the structural, electronic and optical properties of BP, BAs and their (BP) n /(BAs) n superlattices (SLs). The exchange-correlation potential is treated with the local density approximation of Perdew and Wang (LDA-PW). The calculated structural properties of BP and BAs compounds are in good agreement with available experimental and theoretical data. It is found that BP, BAs and their alloys exhibit an indirect fundamental band gap. The fundamental band gap decreases with increasing the number of monolayer n. The optical properties show that the static dielectric constant significantly decreases in superlattices compared to their binary compounds. [Copyright &y& Elsevier]