A simple, effective tight-binding parametrization for Si-Ge interactions on Si(001)

We describe a simple yet extremely effective tight-binding parametrization for Ge-Ge and Si-Ge interactions in near-tetrahedral bonding situations, in particular on the (001) surface of Si and Ge, and present results of tests on various systems (including ad-dimers of Ge and the square structure found during gas-source growth).