Theoretical study of adsortion of Sb on GaAs(110) surface

We present a model for studying the adsorption of Sb atoms on a clean GaAs(110) surface and analyse the consequences of the adsorption on the reflectance anisotropy spectroscopy (RAS). A $1 \times 3$ unit cell is taken as a basis of the Sb-covered GaAs(110) structure. The relaxed coordinates of each configuration have been obtained thanks the use of the ABINIT code [1,2], that is based on pseudopotentials and planewaves. We allow the Sb-covered surface to be disordered by letting every surface atom move freely around its equilibrium position. In order to obtain a representative RAS spectrum of the surface we generate an ensemble with $\cal N$ different structural realizations of the surface and the ensemble RAS average is performed. \newline [1] X. Gonze, et al., Computational Materials Science {\bf 25}, 478 (2002). \newline [2] X. Gonze, et al., Zeit. Kristallogr. {\bf 220}, 558 (2005). \newline [3] Bernardo S. Mendoza, N. Arzate and R.A. V\'azquez-Nava, phys. stat. soli. (c) {\bf 2}, 4031 (2005).