MOLECULAR-DYNAMICS SIMULATIONS OF GAMMA-ALUMINA SURFACE STABILIZATIONBY DEPOSITED SILICON IONS

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