Configurational thermodynamics of vacancy formation in solids by Monte Carlo simulation

Results are reported from a Monte Carlo study of the vacancy formation energy and the configurational vacancy formation entropy in monatomic crystals and in intermetallic compounds as a function of vacancy concentration. Simulations have been carried out for both square and bcc lattices. Although the results have been obtained for the case in which the lattice energy is determined by nearest-neighbour central pairwise interactions only, the results are of more general interest. Contrary to calculations based on the Bragg-Williams approximation, a very significant configurational contribution to the excess vacancy formation entropy may exist at vacancy concentrations often encountered in intermetallic compounds. The vacancy formation energy, often assumed constant in analytical treatments, may also change quite significantly with vacancy concentration.