Transformation Paths in Transition-Metal Disilicides

Abstract

We suggest and investigate three possible displacive transformation paths between the ideal C11b, C40 and C54 structures in MoSi2, VSi2 and TiSi2 by calculating ab initio total energies along these paths. An estimate of transition temperatures based on the calculated energy barriers leads to values comparable with the melting temperatures of the disilicides studied. This confirms their high temperature stability and indicates that if a phase transformation between C11b, C40 and C54 structures of the disilicides takes place, then its prevailing mechanism should be diffusional rather than martensitic like. During the transformations studied, atoms come as close together as, for example, in configurations with interstitials. Hence, the present ab initio results can also help in fitting adjustable parameters of semi-empirical interatomic potentials for the transition-metal disilicides, in particular of the repulsion at short separations of atoms.