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Abstract: A theoretical study of structural, electronic, elastic, thermal and mechanical properties of nonmagnetic intermetallics YM (M=Cu, Zn and Ag), which crystallize in CsCl-type structure, is performed using first principles density functional theory based on full potential linearized augmented plane wave (FP-LAPW) method. The calculations are carried out within the generalized gradient approximation (GGA) for the exchange correlation potential. The calculated ground state properties such as lattice constants, bulk modulus and elastic constants agree well with the experiment. From energy dispersion curves, it is found that these compounds are metallic in nature. The ductility of these intermetallics is determined by calculating the bulk to shear ratio B/G H . The calculated results indicate that YAg is the most ductile amongst the present YM compounds. The results obtained are compared with the available experimental and theoretical results. The mechanical and thermal properties are predicted from the calculated values of elastic constants. [ABSTRACT FROM AUTHOR]

Abstract: We report ab initio calculations of pressure-induced structural phase transition and electronic properties of the NaCl-type actinide nitrides namely AnN (An=Np and Cm). The total energy as a function of volume is obtained using the self-consistent tight-binding linear muffin tin orbital (TB-LMTO) method by performing spin and non-spin-polarized calculations. Magnetically the AnN compounds are stable in ferromagnetic (FM) state at ambient condition. From the present study, we predict a structural phase transition from ferromagnetic (FM) NaCl-type (B1 phase) structure to ferromagnetic CsCl-type (B2 phase) structure for these in the pressure range of 80.0–50.0GPa. The pressure-induced transition is found to be first order. The band structure and density of states (DOS) are reported in both FM-B1 phase and FM-B2 phase. The ground-state properties such as magnetic moment, lattice parameter and bulk modulus are calculated and compared with the available theoretical and experimental results. [Copyright &y& Elsevier]

Abstract: We report a systematic and detailed lattice dynamical investigation on the intrinsic insulating phase of the cobalt oxide superconductor NaCoO2. The phonon dispersion curves, partial and total phonon densities of states are obtained. The calculated Raman, infrared phonon modes and generalized phonon density of states agree reasonably well with the experimental spectra. These studies have enabled an atomic level understanding of the phonon density of states. The effect of Na site occupancy on the phonon spectra are discussed and found significant differences. The lattice specific heat at constant volume and Debye temperature are also reported. The estimated Debye temperature reveals the importance of phonons in the transport properties in the intrinsic insulating phase of the NaCoO2 compound at room temperature. The temperature dependence of the vibrational amplitudes has also been discussed. [Copyright &y& Elsevier]