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In this study we have investigated the robust phase stability, elasto-mechanical, thermophysical and magnetic response of KVSb half Heusler compound by implementing density functional theory (DFT) models in WIEN2k simulation package. The dynamic phase stability is computed in phase type I, II & III phase configurations by optimising their energy. It is observed that given compound is more stable in spin-polarized state of phase type-III. To explore the electronic band structure, we apply the generalised gradient approximation along with Hubbard potential U. The electronic band profile of the Heusler alloy display a half-metallic nature. Moreover, the calculated second-order elastic parameters divulge the brittle nature. To understand the thermodynamical and thermoelectric stability of the alloy at various temperature and pressures ranges Quasi-Harmonic Debye model is executed successfully. The computed value of magnetic moment (MM) found in good agreement with Slater-Pauling rule. Our findings confirms that the predicted half Heusler alloy can be used in various spintronics and thermoelectric applications. [ABSTRACT FROM AUTHOR]

Methylammonium Lead Iodide (MAPbI 3) is bellwether in the field of photovoltaics due to its remarkable optoelectronic properties. However, the instability of MAPbI 3 hinders its commercial scale applications. To address this issue, we have utilized the method of compositional engineering by doping A-site of MAPbI 3 with alkali metals (Na, K, Cs) availing the first principle study within the framework of density functional theory. To realize the band structure, geometry is initially optimized using GGA-PBE, GGA-PBESOL and GGA-PW91 exchange correlation functionals and then GGA + SOC technique is applied to draw the comparison for better insight of the electronic structure. Later we explored the structural, electronic, optical, elastic, and thermodynamic properties of alkali doped MAPbI 3. The results manifest improvement in the phase stability, thermodynamic stability and optical absorption of MAPbI 3 after being doped with Na, K and Cs. These properties can provide research ideas for ensuing research in A-site doped studies of MAPbI 3. [ABSTRACT FROM AUTHOR]

Detailed studies of structural and elastic properties of Fe 2 Ti 1 − x Mn x Al Heusler alloys were carried out using density functional theory within the generalized gradient approximations. In each Heusler alloy, calculations of lattice constants were repeatedly done for successive increases in the lattice constants and the corresponding total energies were recorded. The graphs of the total energy as a function of lattice constant yielded parabolic curves. The present calculations revealed that among the doped alloys, Fe 2 TiAl and Fe 2 Ti 0.75 Mn 0.25 Al exhibit transitions of electrons from valence to conduction bands thereby making these alloys metallic. On the other hand, the ternary and quaternary alloys ( Fe 2 MnAl and Fe 2 Ti 0.25 Mn 0.75 Al respectively) possess half-metallic behavior with direct band gaps of 0.56 eV and 0.41 eV respectively at the Γ -point in the minorities states. To determine the stability of these alloys, the three independent elastic constants in cubic structures (that included C 11 , C 12 , and C 44 respectively) were obtained for all the compositions that confirmed their stabilities. The structural and elastic properties calculations confirmed the stabilities of Fe 2 Ti 0.25 Mn 0.75 Al and Fe 2 MnAl as some new half-metallic materials that can be applicable in spintronic devices. This work revealed the brittleness nature of Fe 2 TiAl and Fe 2 MnAl alloys. [ABSTRACT FROM AUTHOR]

Abstract: Through the assist of the full-potential linear augmented plane wave (FPLAPW) method, the calculations of the electronic band structure, density of states, charge density, Fermi energy and regularity dependent dielectric functions of Cs2KTbCl6 and Cs2KEuCl6 are reported. This study shows that the nature of both these compounds is metallic. The generalized gradient approximations (GGA) exchange correlation potential was applied. The densities of states around Fermi level are frequently subjugated by Eu/Tb-f and DOS below Fermi level are subjugated by Eu/Tb-s/d, Cs-s, Cl-s and K-s/p. The value of the DOS at Fermi level N(E F ) is 17.02 and 4.86 (states per unit cell per eV) for Cs2KEuCl6 and Cs2KTbCl6. The bare electronic specific heat coefficient, is found to be 2.95 and 0.84mJ/molK2 for Cs2KEuCl6 and Cs2KTbCl6, respectively. Three bands crossing the Fermi level along the Γ−A direction of Brillion zone of Cs2KTbCl6 compound and one band crossing along the Γ−A direction of Brillion zone of Cs2KEuCl6 compounds, to form the Fermi surface. There exists a strong hybridization between Tb/Eu-K-p and Cl-s K-s and at −5.0 and −4.0eV. [Copyright &y& Elsevier]

Abstract: The full potential linearized augmented plane wave method within the framework of density functional theory is employed to investigate the structural, thermodynamic and elastic properties of the yttrium chalcogenides (YX: X=S, Se, and Te) in their low-pressure phase ( ) and high-pressure phase ( ). The exchange-correlation potential is treated with the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE). Temperature dependence of the volume and both adiabatic and isothermal bulk moduli is predicted for a temperature range from for the both phases of the herein considered materials. Furthermore, we have analyzed the thermodynamic properties such as the heat capacities, C V and C P , thermal expansion, α, and Debye temperature, Θ D, under variable pressure and temperature. We have calculated the isothermal elastic constants C ij T of the YX monochalcogenides in both NaCl-B1 and CsCl-B2 phases at zero pressure and a temperature range . The results show that rare earth yttrium monochalcogenides are mechanically stable at high temperature. The elastic anisotropy of all studied materials in the two phases has been studied using three different methods. [Copyright &y& Elsevier]

Abstract: We have calculated the on-site Coulomb repulsion (U) for the transition elements Co and Fe. To study the impact of Hubbard potential or on-site Coulomb repulsion (U) on structural and electronic properties the calculated values of U were added on GGA and LSDA. We performed the structure optimization of Co2FeGe based on the generalized gradient approximation (GGA and GGA+U). The calculation of electronic structure was based on the full potential linear augmented plane wave (FP-LAPW) method and local spin density approximation (LSDA) as well as exchange correlation LSDA+U. The Heusler alloy Co2FeGe fails to give the half-metallic ferromagnetism (HMF) when treated with LSDA. The LSDA+U gives a good result to prove that Co2FeGe is a HMF with a large gap of 1.10eV and the Fermi energy (E F) lies at the middle of the gap of minority spin. The calculated density of states (DOS) and band structure show that Co2FeGe is a HMF when treated with LSDA+U. [Copyright &y& Elsevier]

Abstract: We have investigated the structural, electronic and magnetic properties of substitutional europium rare earth impurity in cubic CdS and CdSe by employing the ab-initio method. Calculations were performed by using the full potential linearized augmented plane wave plus local orbitals (FP-L/APW+lo) method within the framework of spin-polarized density functional theory (DFT). The electronic exchange-correlation energy is described by generalized gradient approximation GGA and GGA+U (U is the Hubbard correction). The GGA+U method is applied to the rare-earth 4f states. We have calculated the lattice parameters, bulk modulii, the first pressure derivatives of the bulk modulii and the cohesive energies. The calculated densities of states presented in this study identify the metallic behavior of CdEuS and CdEuSe when we use the GGA scheme, whereas when we use the GGA+U, we see that these compounds are half-metallic. [Copyright &y& Elsevier]

Abstract: Particularly interesting as candidates to technological applications are the manganese perovskites with AMnO3 formula. Their magnetic structure was described as resulting from a particular ordering of the occupied d orbitals which possess. This reflects my understanding of the structural, electronic and magnetic phenomena, which is well established only in the limit where the systems show localized or itinerant electron behavior. In general, the perovskites of ABO3-type are well known with their (anti)ferroelectric, piezoelectric and (anti)ferromagnetism properties applied in considerable technological investigations. In my paper, I studied the ground states properties of the BaMnO3 perovskite oxide. My structural properties are given using LSDA, GGA, LSDA+U and GGA+U in the aim to introduce the exchange correlation potential. In the following paper, I use the GGA+U on the electronic and magnetic properties calculation. I show in my study the density of states, the band structures and also the charge density figures. My results such as lattice parameter, bulk modulus and its pressure derivative agree very well with available theoretical works and experimental data. I discuss the magnetic moment and the U-Hubbard effect introduced by LSDA+U and GGA+U on my results given in this paper. [Copyright &y& Elsevier]

Abstract: The electronic and optical properties of Sb2S3 are studied using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in Wien2k. In this approach, the alternative form of the generalized gradient approximation (GGA) proposed by Engel and Vosko (EV-GGA) was used for the exchange correlation potential. The calculated band structure shows a direct band gap. The contribution of different bands was analyzed from total and partial density of states curves. Moreover, the optical properties, including the dielectric function, absorption spectrum, refractive index, extinction coefficient, reflectivity and energy-loss spectrum are all obtained and analyzed in detail. [ABSTRACT FROM AUTHOR]

Abstract: The electronic and the optical properties of hexaindium heptaselenide In6Se7 have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the Wien2k. In this approach, the alternative form of the generalized gradient approximation (GGA) proposed by Engel and Vosko (EV-GGA) was used for the exchange correlation potential. The calculated band structure shows a direct band gap (Z–Z). The contribution of different bands was analyzed from the total and the partial density of states curves. Moreover, the optical properties including the dielectric function, absorption spectrum, refractive index, extinction coefficient, reflectivity and energy-loss spectrum are all obtained and analyzed in details within the energy range up to 20eV. [Copyright &y& Elsevier]

Abstract: Full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory has been used to calculate structural, electronic and optical properties of Ca1− x Sr x S, an alkali earth chalcogenide, with varying compositional parameter x in the range 0

Abstract: We have performed full potential linear augmented plane wave calculations to investigate the pressure induced phase transition in ZnTe. Total energies of three phases (zinc-blende, cinnabar and Cmcm) are calculated using density functional theory formalism under generalized gradient approximation and Engel–Vosko generalized gradient approximation for the exchange correlation potential approximation. The pressure stability corresponding to zinc-blende, cinnabar and Cmcm phases of ZnTe are computed. We find that cinnabar phase could be formed as a metastable phase by releasing pressure from the high pressure Cmcm phase. The obtained structural, electronic and optical results are compared with previous calculations and available experimental data. Overall good agreement is found. [Copyright &y& Elsevier]

Abstract: We have presented results on the electronic structure and the electric field gradient (EFG) of NpRh3 within a framework of density functional theory within the local density approximation (LDA) and generalized gradient approximation (GGA) with and without spin–orbit coupling (SOC). The electronic density of states (DOS) shows that Np-f to Rh-d hybridization leads to a narrow band 5f-electron. Using the GGA and spinpolarized calculations, the calculated EFG shows that the dominant contribution to EFG comes from electrons with strong p-character. [Copyright &y& Elsevier]

Abstract: We have carried out a first-principles total-energy calculations of the structural and the electronic properties for the series of H-phases compounds Ti2AlC and Ti2AlN. We have applied the full-potential linearized augmented plane waves (FP-LAPW) method based on the density functional theory (DFT) using the local-density approximation (LDA) and/or the generalized gradient approximation (GGA). The quasi-harmonic Debye model, using a set of total energy versus volume calculations obtained with the FP-LAPW method which is applied to study the thermal and vibrational effects. Temperature and pressure effects on the structural parameters, thermal expansions, heat capacities and Debye temperatures are determined from the non-equilibrium Gibbs functions. [Copyright &y& Elsevier]

Abstract: The electronic, structural properties and optical properties of the rutile TiO2 have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2K code. We employed the generalized gradient approximation (GGA), which is based on exchange-correlation energy optimization to calculate the total energy. Also we have used the Engel–Vosko GGA formalism, which optimizes the corresponding potential for band structure calculations. Our results including lattice parameter, bulk modulus, density of states, the reflectivity spectra, the refractive index and band gap are compared with the experimental data. We present calculations of the frequency-dependent complex dielectric function and its zero-frequency limit . [Copyright &y& Elsevier]

Abstract: The structural and electronic properties of X3As4 (X=C, Si, Ge and Sn) compounds were investigated using density functional theory (DFT) calculations. We employed both the generalized-gradient approximation (GGA), which is based on exchange-correlation energy optimization to calculate the total energy and the Engel–Vosko (EV-GGA) formalism, which optimizes the corresponding potential for band structure calculations. The calculated lattice constant, bulk modulus and electronic band structure of pseudocubic X3As4 (X=C, Si, Ge and Sn) compounds are in good agreement with other theoretical results. The analysis shows that the hardest material is C3As4 compound with a bulk modulus B 0=106.5GPa, while Si3As4, Ge3As4 and Sn3As4 have almost the same bulk modulus ranging from 51 to 68.5GPa. Also we have presented the results of cohesive energies and we have given a detail discussion of the bond lengths and bond angles in the pseudocubic phase of group IV arsenides. Furthermore, band structure and density of states calculations show that Si3As4, Ge3As4 and Sn3As4 exhibit a semiconductor behavior with indirect gaps while C3As4 exhibit a metallic behavior using both GGA and EV-GGA. [Copyright &y& Elsevier]

Abstract: The electronic structure and the optical properties of In6S7 crystal are calculated by the first-principles full-potential linearized augmented plane wave method (FP-LAPW) using density functional theory (DFT) in its generalized gradient approximation (GGA). The calculated band structure shows that the In6S7 is a semiconductor with a direct band gap in good agreement with experimental studies. Furthermore, the dielectric tensor and the optical properties, such as absorption coefficient, refractive index, extinction coefficient, energy-loss spectrum and reflectivity, are derived and analyzed in the study. [Copyright &y& Elsevier]

Abstract: By employing the first-principles method of the full potential linear augmented plane waves (FPLAPW), the structural, elastic and the electronic properties of LaBi are investigated. It is found that this compound has a semiconducting small and indirect gap. Through the quasi-harmonic Debye model, in which the phononic effects are considered, we have obtained successfully the thermodynamic properties such as thermal expansion coefficient, Debye temperature and specific heats in the whole pressure range from 0 to 10GPa and temperature range from 0 to 1600K. [Copyright &y& Elsevier]

Abstract: We have applied the full-potential linearized augmented plane wave method (FP-LAPW) within the density functional theory to investigate the structural properties of compound in sodium chloride and wurtzite structures. We have found that the lattice parameter (a) increases with the increment of the In-composition in both structures, while the bulk modulus diminishes with the increase of the In-composition. The lattice constant and the bulk modulus present a small bowing in both structures. We have also analyzed the relative stability of this ternary compound in the two studied phases. We have found that sodium chloride structure is the ground state phase for a In-composition range , while the wurtzite structure is most stable in the range . The results for the binary compounds are in good agreement with the experimental data. [Copyright &y& Elsevier]

Abstract: We present calculations of the structural, and electronic properties of the scandium compounds ScX (X=N, P, As and Sb). They are based on the generalized gradient approximation (GGA) within the density functional theory (DFT), employing the first-principles, full potential-linearized augmented plane wave (FPLAPW) method. Bulk properties, including lattice constants, bulk moduli and derivatives, cohesive energies, and band structure are reported in both NaCl (B1) and CsCl (B2) structures. The transition pressure for the NaCl-type to CsCl-type is calculated to be about 364.32, 245.61, 92.40 and 39.78GPa for ScN, ScP, ScAs and ScSb, respectively. We show that our results are in agreement with the available experimental data and the first-principles theoretical studies. [Copyright &y& Elsevier]

Abstract: We investigate the electronic properties of the hexaindium heptasulfide In6S7, employing ab initio calculations based on density functional theory using in the first time the full-potential linearized augmented plane wave method with the generalized gradient approximation for the exchange and correlation potential. On the other hand, we present the same results obtained by the linear muffin-tin orbital method. Band structure, total and partial density of states, effective masses and ionicity factor are analyzed. The bonding nature of this material is analyzed from the density of states. We found that the In6S7 is a semiconductor with a small gap of about 0.7eV. [Copyright &y& Elsevier]

Abstract: We present first-principles of the full-potential linearized augmented plane wave calculations of the effect of hydrostatic pressure on the optical properties of zinc-blende GeC, SnC and GeSn compounds. The refractive index and its variation with hydrostatic pressure are well described. An accurate calculation of linear optical functions (refraction index and its pressure derivative, and both imaginary and real parts of the dielectric function) is performed in the photon energy range up to 15eV. The predicted optical constants agree well with the available experimental and theoretical ones. [Copyright &y& Elsevier]

A theoretical study of structural and electronic properties of GeC, SnC and GeSn is presented using the full potential linearized augmented plane wave method. In this approach, the generalized gradient approximation was used for the exchange–correlation potential. Results are given for lattice constant, bulk modulus and its pressure derivative in both zinc-blende and rocksalt structures. Band structure, density of states and band gap pressure coefficients in zinc-blende structure are also given. The results are compared with previous calculations and with experimental measurements. [Copyright &y& Elsevier]

Magnetic properties of stable iron-based compounds (FeMnP 1-x A x (A = Si, In, Se and Sn) were investigated by use of Quantum Espresso (QE) within the Density Functional Theory (DFT) formalism as a viable magnetic refrigerant. In this research work, DFT technique was the first principle theoretical approach that was employed along with the planewave pseudopotentials (ultrasoft), and the projected augmented wave (PAW) within the generalized gradient approximation (GGA) to describe the electronic structure and investigation of magnetic properties. Magnetic stability is described as the repeated magnetic performance of a material under specific conditions over the life of a magnet. In this case our reference compound, FeMnP 0.67 Si 0.33 was optimized and its properties were examined in both ferromagnetic (FM) and antiferromagnetic (AFM) states. Two Si atoms were later substituted with atoms of post-transitional metals in period four and five which has shown first-order magnetic transition at near room temperatures. In, Se and Sn were chosen to replace silicon since they would easily mimic the bond, their availability and nontoxic nature. The results showed that only ferromagnetic states of both host and doped compounds gave promising magnetic properties that can be applied in magnetocaloric effect phenomenon. Their band structure results indicated that they were all metals. Antiferromagnetic states showed no magnetic properties as the spin-polarized graph resulted in perfect symmetry of spin up projected density of states (PDOS) and spin down PDOS. From the thermo_pw calculations, it was realized that FeMnP 0.67 In 0.33 is the best candidate for near room temperature magnetic refrigeration among the studied compounds. [ABSTRACT FROM AUTHOR]

Theoretical calculations of Al 0·75 Co 0·25 Sb diluted magnetic semiconductor (DMS) were investigated by using both GGA and TB_mBJ methods. First, the energy-volume optimization curves of AlAs and Al 0·75 Co 0·25 Sb compounds were plotted and the ferromagnetic (FM) phases were observed to be more energetically stable. The spin-up states showed metallic properties while the spin-down states had a semiconductor nature. While these properties did not change, some differences were observed in the band gap values. Fermi energies were calculated as 0.298 and 0.462 R y and band gap values were obtained as 0.229 and 0.855 eV by using GGA and TB_mBJ methods, respectively. The values of the total magnetic moments did not change and they were obtained as 2.00 μ B /f.u. in both methods. Finally, the elastic properties of Al 0·75 Co 0·25 Sb compound were calculated. According to these results, Al 0·75 Co 0·25 Sb compound is a brittle half-metal ferromagnetic material and it is suitable for use in spintronic applications. • The ferromagnetic (FM) phase is the most stable energetically. • The total magnetic moment of Al0·75Co0·75Sb DMS is 2.00 μB/f.u. • The band gap is 0.229 eV in GGA method. • The band gap is 0.855 eV in TB_mBJ method. • According to elastic calculations, Al0·75Co0·75Sb DMS is brittle half-metal ferromagnetic material. [ABSTRACT FROM AUTHOR]

UBe13 is a typical heavy-fermion superconductor compound. The energy band structure and the Fermi surface for UBe13 are calculated by the relativistic linear APW method. The Fermi surface is found to consist of two hole sheets and one electron sheet. These sheets of the Fermi surface are all small in size and closed in topology. The generalized gradient approximation is also applied to the energy-band calculation of UBe13. These results are compared with those of the conventional LDA calculation. [Copyright &y& Elsevier]

Abstract: Iron monosilicides (FeSi) is an important material with very interesting properties that can be harnessed for technological applications. Our attention has been drawn to the so-called first principle study of the electronic and thermodynamic properties of B2-FeSi by Zhao et al. (Physica B 406 (2011) 363–367) using pseudopotential plane wave method. They reported that FeSi in B2 phase is a narrow band gap material with a band gap of 0.05eV using a generalized gradient approximation (GGA) potential implemented within the density functional theory (DFT) approximation. This comment comes to address an important oversight by these authors in the interpretation of their results. [Copyright &y& Elsevier]