Atomic geometries of InP(110)-Sb(1 ML) and GaAs(110)-Sb(1 ML)

Using the ab initio molecular-dynamics method I have calculated the equilibrium atomic geometry for a monolayer coverage of Sb on InP (110) and GaAs (110) surfaces. For the ‘‘epitaxial continued layer structure’’ the absorption of Sb almost completely removes the relaxation of the clean surfaces. For Sb/GaAs the overlayer is characterized by a tilt angle of ${\mathrm{\omega }}_1$=1.2° and a vertical shear of ${\mathrm{\Delta }}_{1,\mathrm{\perp }}$=0.04 Å. For Sb/InP I have calculated ${\mathrm{\omega }}_1$=4.3° and ${\mathrm{\Delta }}_{1,\mathrm{\perp }}$=0.15 Å. The predicted structural parameters are in remarkable agreement with the recent results obtained via low-energy electron diffraction intensity analyses. Our results for Sb/InP are, however, found to be quite different from those obtained from an earlier tight-binding calculation. It is further shown that the Sb-Sb, Sb-cation, and Sb-anion bond lengths are in agreement with the concept of Pauling’s bond radii.