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The first principles calculations of structural and magnetic properties of the Heusler material Mn2NiAl, have been studied using a full potential linearized augmented plane wave (FP-LAPW) within the density-functional theory (DFT). The phase stability of the cubic austenitic (L21) structure for Mn2NiAl in both Cu2MnAl (Fm3 m space group) and Hg2CuTi (F43 m space group) type of structures with ferromagnetic and antiferromagnetic states, has been treated by applying the generalized gradient approximation proposed by Wu and Cohen (WC-GGA) alongside with the martensitic structure of Mn2NiAl. The analysis of phase stability, cohesive energy and the calculated formation enthalpy of Mn2NiAl reveal that the ferromagnetic MnMnNiAl is the most stable type of structure. Moreover, the calculated lattice parameters are found to be in good agreement with theoretical data. The variation of total magnetic moments MT(μB), MMn (μB), MNi (μB) and MAl (μB) in Mn2NiAl with pressure at varying temperature (0, 273 and 344 K), have been calculated. [ABSTRACT FROM AUTHOR]

The principal purpose of this work is to further the understanding of the structural, electronic, and thermodynamic properties of the SrxCa1-xS alloys (0≤ x ≤1) in Rock-salt phase using the full potential augmented plane wave (FP-LAPW) method within density functional theory. The exchange-correlation potential for structural properties was calculated by the standard local density approximation (LDA) and GGA (PBE) and the new form of GGA (WC) which is an improved form of the most popular Perdew-Burke-Ernzerhof (PBE), while for electronic properties, the alternative form of GGA modified by Becke-Johnson exchange correlation potential (MBJ) was also applied. It is shown that investigation on the effect of composition on lattice constant, bulk modulus, and band gap for ternary alloys shows almost nonlinear dependence on the composition. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing ΔHm as well as the phase diagram. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: Using first-principle method, we investigate the structural, electronic, optical and thermodynamic properties of the strontium semiconductors Pb1− x Sr x S with 25%, 50% and 75% of Sr. The calculations are performed by using the full-potential linearized augmented plane wave (FP-LAPW) method. As exchange–correlation potential we used the generalized gradient approximation (GGA) of Perdew et al. The variation of the calculated equilibrium lattice constant versus concentration shows that a small deviation from Vegard’s law is clearly visible with downward bowing parameter equal to 0.009Å. The bulk modulus as a function of x for Pb1− x Sr x S alloy shows a significant deviation from the linear concentration dependence (LCD) with downward bowing equal to 6.62GPa. The different roles of structural and chemical effects on the gap bowing and its variation with composition are identified and discussed. In addition, density of states and optical properties were calculated and compared to the available experimental data and previous theoretical works. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing ΔH m as well as the phase diagram. [ABSTRACT FROM AUTHOR]

Abstract: The structural, electronic and thermodynamic properties of the SrS1– x O x ternary mixed crystals have been studied using the ab initio full potential linearized augmented plane wave (FP-LAPW) method within density functional theory. The effect of composition on lattice parameter, bulk modulus and band gap was investigated. The lattice constants from Vegard''s law and the bulk modulus from linear concentration dependence were observed for the alloys. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. The thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing as well as the phase diagram. In addition to FP-LAPW method, the composition dependence of the refractive index and the dielectric constant was studied by different models. [Copyright &y& Elsevier]

Abstract: The ab initio full potential linearized augmented plane wave (FP-LAPW) method within density functional theory was applied to study the structural and electronic properties of the compounds SrS, SrSe, SrTe and their alloy SrS1−xSex in the NaCl structure. Results are obtained using both the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange-correlation potentials. The ground-state properties, like lattice constant and bulk modulus obtained from our calculations agree very well with experimental and other theoretical calculations. We present the main features of electronic properties, where the electronic band structure shows that the fundamental energy gap is indirect . Moreover the alternative form of GGA proposed by Engel and Vosko (GGA-EV) is also used for band structure calculations. Results obtained with this approximation show that significant improvement over other theoretical work are closer to the experimental data. The effect of composition on lattice parameter and bulk modulus was investigated. Deviations of the lattice constant from Vegard’s law and the bulk modulus from linear concentration dependence were observed for the alloy. Moreover, the microscopic origins of the gap bowing were explained. In addition the thermodynamic stability of the alloy was investigated by calculating the critical temperature for SrS1−xSex alloy. [Copyright &y& Elsevier]