Total energy and electronic structure calculations of C15 Laves-phase compounds MV₂ (M=Zr, Hf or Ta): Elastic properties

Abstract

The total energy and electronic structure of early-transition-metal cubic Laves-phase compounds MV₂ (M─Zr, Hf or Ta) have been calculated using the linear muffin-tin orbital method within the local-density and atomic sphere approximations. The elastic properties of the compounds have been examined from these results. The bulk moduli of the cubic MV₂ alloys (M─Z, Hf or Ta) obtained from the total-energy calculations are 162, 172 and 218 GPa respectively. It is found from the electronic structures that there is a double degeneracy of electron energy levels with a linear dispersion relationship in the neighbourhood of the X point of the Brillouin zone and that the Fermi surfaces of the alloys pass near X-point of the Brillouin zone with an energy gap Δε. The contribution c^(e) ₄₄ from these electrons to the shear modulus c₄₄ of the alloys, is found to be anomalous at high temperatures (T>400K), such that c^(e) ₄₄ increases with increasing temperature.