Binding sites for SiH2/Si(0 0 1): A combined ab initio, tight-binding, and classical investigation

Binding sites for SiH2 on Si(0 0 1) are investigated theoretically by using several different methods. Possible local minima are first sampled by classical molecular dynamics simulations of the SiH2/Si(0 0 1) impact, allowing for a preliminary, fast selection. A further refinement is carried out by geometry optimizations using semiempirical tight-binding and density functional theory calculations, based on both the local density and generalized gradient approximations. In most cases only minor morphological changes are obtained when comparing the ab initio sites with the classical potentials and tight-binding ones. The purely classical treatments here tested, however, overestimate the number of minima and fail in accurately reproducing the relative energy of some of the adsorption sites. Closer agreement is obtained with tight-binding, with the noticeable exception of the lowest ab initio minimum (on-dimer site).