Super-cells which consisted of 63 or 64 atoms were used to evaluate lattice relaxation at vacancies in this material by using plane waves with soft or hard pseudopotentials. Car-Parrinello molecular dynamics calculations were performed which permitted both nearest-neighbor and second-nearest neighbor atoms to move. The results were compared with static calculations in which only the atoms that were nearest to the vacancy were assumed to move.

D.P.Joubert, L.Li, J.E.Lowther: Solid State Communications, 1996, 100[8], 561-3