Ab initio study of metastability in refractory metal based systems

The interplay between local atomic environment and phase stability properti es for tetrahedrally close packed (tcp) structures in transition metals has been examined using first-principles methods. The most probable transitory metastable tcp phases solidifying from undercooled transition metal melts and the sequence as a function of composition of tcp phases observed in the phase diagrams of many transition metal alloys are shown to have a common origin. These phenomena are explained in terms of atomic coordination and l evel splitting of the d-like states.