High-order reconstructions of the Ge(100) surface

Abstract

We have performed ab initio density-functional calculations of total energies of the Ge(100) surface to compare the ground states of (2\ifmmode\times\else\texttimes\fi{}1), c(4\ifmmode\times\else\texttimes\fi{}2), p(2\ifmmode\times\else\texttimes\fi{}2), and p(4\ifmmode\times\else\texttimes\fi{}1) symmetry dimer reconstructions. We find that p(2\ifmmode\times\else\texttimes\fi{}2) and c(4\ifmmode\times\else\texttimes\fi{}2) are the lowest-energy reconstructions and are nearly degenerate in energy. From these ab initio total energies, we compute the coupling constants for a model Hamiltonian for the surface and predict the phase-transition temperature from either an ordered c(4\ifmmode\times\else\texttimes\fi{}2) or p(2\ifmmode\times\else\texttimes\fi{}2) state to a disordered buckled b(2\ifmmode\times\else\texttimes\fi{}1) state.