AMORPHIZATION OF A SUBSTITUTIONAL BINARY ALLOY - A COMPUTER EXPERIMENT

A novel route towards amorphization of an initially crystalline structure is explored by molecular dynamics simulations of a two-dimensional model of 'soft-disk' atoms. Amorphization is driven by a slow increase in the diameters of half the atoms, chosen at random on an initially monodisperse triangular lattice, and a simultaneous reduction in size of the remaining atoms, keeping constant a suitably chosen mean diameter as well as the temperature. The crystal is found to undergo a discontinuous transition towards an amorphous solid at a critical size ratio of the two species. The transition is signalled by jumps of a number of order parameters characterizing the loss of long-range positional and bond-orientational order, and by hysteresis reminiscent of a first-order phase transition. At higher temperatures, a similar adiabatic change in the size ratio leads to melting.