The dynamics of Al dimers on (111) surfaces, under equilibrium and compression conditions, were studied by using first-principles density functional theory calculations. Unexpected ground states were predicted, for the strained and unstrained dimers, which were expected to be easy to verify by using scanning tunnelling microscopy to measure dimer directions and heights. It was found that Al dimers were stable at up to about 220K, and migrated via concerted sliding at temperatures above 50K. A rotational type of motion was already activated at about 8K, but did not lead to diffusion. By performing molecular dynamics simulations, it was concluded that elastic, rather than electronic, effects ruled out free rotors. A marked compression-mediated decrease in diffusivity offered a means for affecting epitaxial growth by straining.

Al Dimer Dynamics on Al (111) A.Bogicevic, P.Hyldgaard, G.Wahnström, B.I.Lundqvist: Physical Review Letters, 1998, 81[1], 172-5