TRACER DIFFUSION OF OXYGEN IN 123YBCO FROM MONTE-CARLO SIMULATIONS OF THE ASYNNNI MODEL

摘要

The self-diffusion of oxygen in 123YBCO was studied by means of computer simulations of a two-dimensional lattice model. The tracer diffusion coefficients were calculated from samples of lattice configurations at equilibrium for given values of the temperature and the oxygen concentration. In obtaining these samples both random and ordered initial lattice configurations were used. Regardless of the fact that the simulations from ordered initial configurations do lead to different samples from those obtained for a random start (notably for lower temperatures), the diffusion coefficients do not change significantly. In particular, the strong dependence of the diffusion coefficients on the oxygen concentration, found by previous workers for more uniform configurations, persists even for our nonuniform configurations.