Ab initio calculation of the structural, mechanical and thermodynamic properties of Beryllium Sulphide (BeS)

An ab initio plane-wave Pseudopotential calculations using the density functional theory (DFT) implementing the generalised gradient approximation (GGA) to study the structural, elastic constants, phonon dispersion curves, density of state and thermal properties of BeS. Also we calculated the shear modulus, Young’s modulus, Poisson’s ratio, and the Zener’s anisotropic factors. The calculated properties are agreement with previous experimental and theoretical results. The quasi-harmonic approximation is applied to determine the thermal properties, and these properties are in good agreement with available literatures. The major results of the properties determined were discussed.Keywords: Poisson’s ratio, Plane-Wave Pseudopotential, Quasi-Harmonic Approximation, Lattice Paramete

Phonon Dispersion of Alkali Metals Using the TB-SMA Model of Cohesion

The determination of Phonon dispersion of alkali metals was unsuccessful using the parameter n=1/2 or 2/3 in the past two decades. In this study the parameter n has been consistently determined for the different alkali metals, the force constant has been determined up to the fourth next nearest neighbour. The result showed that the TB-SMA dispersion curves were in good agreement with experiment. This good agreement with experiment of the TB-SMA Phonons counters the prevailing notion in the literature that the TB-SMA model fails for alkali metals