Monte Carlo Simulation of Alloy Phase Diagrams and Short-Range Order

Abstract

As a prototype model for order-disorder phenomena in binary alloys, a face-centered cubic lattice is considered,the sites of which can be taken by either A-atoms or B-atoms, assuming pair-wise interactions between nearest (J) and next nearest neighbours (J). The phase diagram is constructed from Monte Carlo calculations. Some technical aspects essential for the success of such calculations are briefly mentioned (use of grand-canonical rather than canonical ensemble, how to obtain the free energy needed to locate first-order phase transitions, etc.). It is shown that the topology of the phase diagram changes when the ratio R = J_nnn/J_nn is varied, and this behaviour is discussed in the context of approximate calculations (mean field, cluster variation method) and renormalization group predictions. The temperature variation of some Cowley short-range order parameters is compared to pertinent experiments on the Cu-Au system.