Computer simulation of de-mixing in solid solution oxides

Abstract

De-mixing of the oxide solid solution (Co, Mg)O under an oxygen potential gradient by cation vacancy diffusion has been studied by Monte Carlo computer simulation. Because oxygen ions are practically immobile and form a rigid lattice, the de-mixing process can be simplified to cation diffusion under a vacancy concentration gradient in a random alloy. When the same parameters and boundary conditions were employed as those by Schmalzried et al., Akbar et al. and Vedula the simulation results showed excellent agreement with those of experiments, phenomenological approaches and analytical statistical mechanical investigations. The agreement with experiment could be illusory. When independent experimental values of cation vacancy concentrations and exchange frequency ratios were used in the simulation, the agreement between the simulation and the experimental de-mixing results deteriorated. Allowance for errors in the independent values provides sufficient room for agreement however.