First-principles calculations of the interaction of H with the close-packed (00•1) surface revealed that adsorbed H reduced the barriers and formation energies of surface defects. It was found that a H atom that was adsorbed on top of an adatom reduced its surface diffusion barrier by a factor of 3. The preferential binding of H to surface defects reduced the formation energy of steps, adatoms and vacancies on (00•1). Because H adatoms repelled each other on the flat surface, but not when adsorbed at the present defects, the formation of these defects was especially easy at high H coverages. The results explained the experimental observation that H-induced vacancy reconstructions, which predominated at high H coverages, formed at temperatures that were as low as 100K.

R.Stumpf: Physical Review B, 1996, 53[8], R4253-6