MOLECULAR-DYNAMICS SIMULATIONS OF ALPHA-ALUMINA AND GAMMA-ALUMINA SURFACES

Molecular dynamics simulations of crystalline aluminum oxide were perf ormed for alpha-Al2O3 and gamma-Al2O3 phases. Both bulk crystals and s urfaces of each phase were studied. For each of the surfaces, several possible atomic terminations were examined and surface energies, densi ty profiles, and atom configurations have been calculated. It was foun d that due to processes of surface relaxation and reconstruction some terminations of the alpha-alumina surfaces become more likely to appea r. For gamma-alumina, the occurrence of cation vacancies in the crysta l structure has a significant influence on surface morphology. On the surfaces, additional active sites were observed which are not predicte d by idealized models which omit vacancies.