Simulation of As_2 adsorption on GaAs

Animation illustrating the use of Density Functional Theory for studying problems in materials science (see also: P. Kratzer and M. Scheffler, Computers in Science & Engineering 3, No. 6, 16-25 (2001) ). As part of an investigation of the elementary processes in molecular beam epitaxy of GaAs, the chemical reaction of As_2 molecules with the GaAs(001) surface is studied. Lower left: Structural model with As_2 molecule (blue dumpbell) approaching the beta2(2x4)-reconstructed GaAs(001) surface. Ga atoms are shown as green balls, and As atoms as blue balls. Lower right: Calculated valence electron density (yellow/brownish iso-contour surface) superimposed on the structural model. The chemical reaction shows up as a merger of the As_2 valence electron density (moving blob) with the surface electron density. Upper right: Electronic density of states (arbitrary units) projected onto the 4s (red curve) and 4p (yellow curve) orbital of an As atom in the As_2 molecule, plotted as a function of the Kohn-Sham energy of the electronic states. Changes in the position and the shape of the peaks are indicative of changes in the bonding character of the orbitals as the reactions proceeds