ATOMIC GEOMETRY AND ELECTRONIC-STRUCTURE OF S INP(001)/

We have performed ab initio pseudopotential calculations of the atomic geometry and electronic states for a monolayer S-covered (001) surfac e of InP. It is found that for the 1 x 1 periodicity with S in the bri dge site, the overlayer-substrate distance between S and In is 1.3 Ang strom and the In-S-In angle is 113.8 degrees. While the calculated In- S-In angle is close to the experimentally deduced value, we find that our prediction of overlayer-substrate distance is smaller than the val ue obtained from LEED analysis. We also discuss the energetics of form ation of long and short dimer bonds for the 1 x 2, 2 x 1 and 2 x 2 rec onstructions of the surface.