The temperature-dependent elastic properties of B2-MgRE intermetallic compounds from first principles

Abstract

The temperature-dependent elastic modulus of MgRE (RE=Y, Dy, Pr, Sc, Tb) intermetallics with B2-type structure are presented from first-principles quasistatic approach, in which the static volume-dependent elastic constants are obtained by the first-principles total-energy method within density functional theory and the thermal expansion is obtained from the quasiharmonic approach based on density-functional perturbation theory. The comparison between the predicted results and the available experimental data for a benchmark material NiAl provides good agreements. At T=0 K, our calculated values of lattice parameter and elastic moduli for MgRE intermetallics show excellent agreement with previous theoretical results and experimental data. With temperature increasing, we find that the elastic constants satisfy the stability conditions for B2 structures and follow a normal behavior with temperature, i.e., decrease and approach linearity at higher temperature and zero slope around zero temperature. In addition, the sound velocities as a function of temperature for the NiAl and MgRE intermetallics are calculated and the relations to phonon spectrums have also been discussed.