TOTAL-ENERGY AND ELECTRONIC-STRUCTURE CALCULATIONS OF C-15 LAVES-PHASE COMPOUNDS MV2 (M=ZR, HF OR TA) - ELASTIC PROPERTIES

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 = Zr, 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 DELTAepsilon. The contribution c44(e) from these electrons to the shear modulus c44 of the alloys, is found to be anomalous at high temperatures (T > 400 K), such that c44(e) increases with increasing temperature.