A parametrized tight-binding molecular dynamics scheme was used to study vacancies on the (001) c(4 x 2) surface. Simulated annealing was performed by using a fictitious Lagrangian procedure to determine the optimum structure of a single vacancy and of a dimer vacancy on this surface. It was found that a mono-vacancy was less stable than a dimer vacancy; in agreement with experimental observations. It was also shown that there was a possible anisotropy in the surface migration of a dimer vacancy on the surface. The calculated activation energy for dimer diffusion was 0.6eV higher than that which had been estimated experimentally at high temperatures.

K.C.Low, H.S.Lim, C.K.Ong: Journal of Physics - Condensed Matter, 1994, 6[45], 9551-60