MOLECULAR-DYNAMICS SIMULATIONS OF GAMMA-ALUMINA SURFACE STABILIZATION BY DEPOSITED SILICON IONS

Molecular dynamics simulations of the pure and doped surfaces Of gamma-alumina have been performed. An onset of surface diffusion is observed in the pure samples near the temperature of 1200 K. The instability is caused by the cation vacancies adjacent to the surface. Silicon ions deposited into the vacancies reduce mobility of the surface ions and prevent the onset of diffusion. This forms a microscopic picture of the role of additives in stabilization of the gamma-alumina surfaces. Presence of the vacancies and their closing by the dopant ions also enables a new interpretation of the recent LEIS data.