ATOMIC-STRUCTURE OF THE NA SI(100)-(2X1) SURFACE

Abstract

The adsorption geometry of Na in a half-monolayer coverage on the symmetric-dimer Si(100)-(2 X 1) surface is studied by carrying out pseudopotential density-functional total-energy calculations. We find that the valley-bridge site is the most stable adsorption site and that the corresponding equilibrium Na-Si bond length is 2.94 angstrom. The partial-core correction to the Na pseudopotentials increases the Na-Si bond length by about 0.2 angstrom, but doesn't change the site preference. The present calculations are in good agreement with the pseudopotential result of Zhang et al.[3] which was in conflict with the earlier pseudopotential result of Batra.[2]