Instabilities on crystal surfaces: The two-component body-centered solid-on-solid model

Abstract

The free energy of crystal surfaces that can be described by the two-component body-centered solid-on-solid model has been calculated in a mean-field approximation. The system may model ionic crystals with a bcc lattice structure (for instance CsCl). Crossings between steps are energetically favored, which leads to the formation of networks of steps and of sharp edges between facets and rounded areas. There is a strong tendency to faceting even at finite temperatures, as seen experimentally in simple cubic ionic crystals (NaCl). Transfer-matrix calculations corroborate these results.