Simulations of adatom geometries on the Si(111) surface using a model potential

To deal with the large bond-angle distortions found in adatom $T_4$ and $H_3$ geometries on the Si(111) surface and elsewhere, the empirical potential of Khor and Das Sarma is extended by making use of the results of ab initio total-energy calculations of two $H_3$ adatom configurations. The potential is applied to other $H_3$ and $T_4$ configurations, the 1×1 surface reconstruction, the Pandey π-chain model, and the Si(100) dimer reconstruction. The results are in good agreement with ab initio calculations. The extended potential should be useful in the study of other surface reconstructions where large bond-angle distortions are present.