a b s t r a c tStructural properties, electronic band structure, real and imaginary parts of complex dielectric function of alkali chloride XCl (K, Rb and Li) compounds were investigated under various pressures using first principles calculations. Moreover, Gibbs free energies were also calculated at those pressures. Calculated results of the Gibbs free energy show that LiCl does not show any structural phase transition. However, structural phase transitions of KCl and RbCl occur from NaCl (B1) to CsCl (B2) at 4.5 and 1.7 GPa pressures, respectively. The electronic band gaps under pressure were also calculated. The calculated physical properties of these compounds are compared with the previous theoretical and experimental results and a good agreement was observed.

Abstract:Using the first-principles band-structure method, we have calculated the structural and electronic properties of zincblende TlAs, TlP, GaAs and GaP compounds and their new semiconductor Tl Ga 1− As P 1− quaternary alloys. Structural properties of these semiconductors are obtained with the Perdew and Wang local-density approximation. The lattice constants of Tl Ga 1− As, Tl Ga 1− P ternary and Tl Ga 1− As P 1− quaternary alloys were composed by Vegard's law. Our investigation on the effect of the doping (Thallium and Arsenic) on lattice constants and band gap shows a non-linear dependence for Tl Ga 1− As P 1− quaternary alloys. The band gap of Tl Ga 1− As P 1− , E ( ) concerned by the compositions and . To our awareness, there is no theoretical survey on Tl Ga 1− As P 1− quaternary alloys and needs experimental verification. 71.15.Mb, PACS (2008): Keywords:density functional theory • electronic structure of disordered solids • electron density of states and band structure of crystalline solids © Versita sp. z o.o.

a b s t r a c tIn this paper, we investigated electronic, optic, elastic, dynamic and thermodynamic properties of RbAu compound by density functional theory within the generalized gradient approximation. The calculated static value of real part of dielectric constant is 6.7. The calculated electronic band structure of RbAu shows that RbAu is a semiconductor with an indirect band gap of 0.36 eV. Besides, RbAu obeys mechanical stability and it demonstrates elastic anisotropy. 540K is classical limit for specific heat of RbAu.

The lattice parameters, bulk modulus, first derivative of the bulk modulus, electronic band structures, phonon dispersion curves and phonon density of states calculations for Li2AlGa and Li2AlIn Heusler alloys are performed and compared in this study using density functional theory within the generalized gradient approximation. Computed lattice parameters display a good agreement with the literature. Obtained electronic band structures of both Heusler alloys show that they are in semi-metallic structure. Phonon dispersion curves and the phonon density of states graphs are also obtained in order to study the lattice dynamics of these Heusler alloys. It is noticed that Li2AlGa and Li2AlIn Heusler alloys are dynamically stable in the ground state.

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The magnetic properties, martensitic transformation characteristics, the magnetic field-induced transformation characteristics, and super spin-glass behaviour at low temperature of Ni46.86Co2.91Mn38.17Sn12.06 (at. %) magnetic shape memory alloys (MSMAs) were investigated under various magnetic field levels over temperature intervals from 400 K to 10 K. We observe a small magnetization difference during the martensitic transition evidenced with a visible thermal hysteresis. To investigate the magnetic field induced phase fraction, the minimum magnetic field required to start and complete the magnetostructural phase transition is computed. Super-spin glass features in magnetic data are observed that interacting magnetic clusters are frozen below a critical temperature. Magnetization is computed as a function of temperature at various constant fields using molecular field theory. The critical exponent, β is deduced for the temperature-induced magnetization, which indicates that the MSMA exhibited ferromagnetic ordering during field-cooling and on heating an antiferromagnetic ordering at low temperatures and in low applied magnetic fields. These observations are consistent within the framework of an Ising or Heisenberg model.

We report a study of structural, electronic and dynamic properties of Li 3 Bi and Li 2 NaBi via density functional theory. It is found that Li 3 Bi and Li 2 NaBi show semiconducting property with an indirect electronic band gap. The calculated structural and electronic parameters (lattice parameters, bulk modulus, bulk modulus derivation) are in a good agreement with the available experimental data. Full phonon spectra of Li 3 Bi and Li 2 NaBi materials in the Rock Salt structure were collected using the linear response method. At 0 GPa pressure, Li 3 Bi is dynamically stable while Li 2 NaBi, which can be synthesized from Li 3 Bi by replacing one Bi atom with the Na atom, is unstable. In this study we searched to find the pressure value that makes Li2NaBi dynamically stable. Calculations showed that the Li 2 NaBi structure becomes stable when 8.62 GPa pressure is applied to the Li 2 NaBi structure. This study is thought to give direction to the future studies.