Ab initio calculations of elastic constants and thermodynamic properties of NiAl under high pressures

We have investigated the structural and elastic properties of NiAl under high pressures using norm-conserving pseudopotentials within the generalized gradient approximation correction (GGA) in the frame of density functional theory. The calculated pressure dependence of the normalized volume is in excellent agreement with the experimental results. The elastic constants and anisotropy as a function of applied pressure, the ratio of the normalized volume V/V0 with the applied pressure are presented. The variations of bulk modulus, anisotropy and the brittleness with the pressure are investigated. Through the quasi-harmonic Debye model, we also study the thermodynamic properties of NiAl. The thermal expansion versus temperature and pressure, the thermodynamic parameters (Debye temperature and specific heat) with pressure P, and the heat capacity of NiAl at various pressures and temperatures are estimated.