Spin polarization and the energetics of chlorine adsorption on the GaAs(110) surface

We have investigated the energetics of chlorine adsorption on the GaAs(110) surface using first principles plane-wave pseudopotential calculations. Both spin-polarized and spin-compensated calculations were performed for a set of eight different configurations of adsorbed chlorine atoms. We find that spin polarization plays an important role in the energetics of adsorption, particularly when we compare chlorine adatom binding energies for configurations with different numbers of "half-filled" dangling bonds. Our calculations show that scanning tunneling microscopy data of chlorine adatom configurations, with observations of islands at lower temperatures and chains at higher temperatures, can be understood in terms of the energetics. Previous calculations, which did not include spin-polarization effects, were not able to provide a definitive conclusion on these observations. From the energetics of the various configurations studied, we can extract a set of effective lateral interaction parameters between chlorine atoms adsorbed on GaAs(110). However, analysis of this set of parameters shows that the range of the effective lateral interactions probably extends to larger distances than the unit cells used in our calculations. (C) 1998 American Institute of Physics. [S0021-9606(98)70140-0].