We have performed ab initio calculations of the atomic structure and energetic stability of the Bi-covered InAs(110) surface. The calculations were performed within the density-functional theory, using norm-conserving fully separable ab initio pseudopotentials. Two experimentally proposed structural models have been considered: (1×1)-ECLS and (1×2). Our total energy calculations indicate that the formation of the (1×2) model is energetically more favourable than the (1×1) model by 41 meV/(1×2). The calculated equilibrium geometries, for the InAs(110)-Bi(1×1) and -Bi(1×2) surfaces, show in general a good agreement with the experimental x-ray measurements carried out by Betti et al.

We have performed first-principles total energy calculations to investigate the adsorption process of Ge on Si(001)/Te, and the surfactant action of Te during the epitaxial deposition of Ge on Si(001)/Te, based on an atomic exchange process, Ge <-> Te. The total energy calculation indicates that the adsorption of Ge atom in "vacancy" site is energetically more favourable than its adsorption in "bridge" site. The adsorption of Ge in "on-top" and "anti-bridge" sites can be ruled out. The segregation process of Te atoms, based on an atomic exchange mechanism, reduces the total energy of the surface, confirming the surfactant effect of Te atoms.