Atomistic simulation of the surface energy and structure of the clean and hydrated surfaces of spinel MgAl_2O_4

摘要

Atomistic simulations with atomic potentials including anion polarisibility have been performed for the clean surfaces as well as the dissociative adsorption of water on spinel-MgAl_2O_4 with various terminations. The calculations show that for the most stable surface the clean surface energy is 2.27 J/m~2 for the {100}, about 2.85 J/m~2 for the {110}, and 3.07 J/m~2 for the {111} orientation. The dissociative adsorption of water on the surfaces is generally energetically favorable. For the {110} and {111} orientations the surfaces cleaved between oxygen layers show high absorption and stability. For the clean surface, structure relaxation was found, while such relaxation was reduced after water absorption. It is suggested that during fracture only partially hydration occurs, leading to cleavage preferentially along the {100} orientation.