Preroughening of crystal surfaces and energy differences between inside and outside corners

Solid-on-solid models provide a comprehensive description of surface roughening, preroughening, and reconstruction. Au(110) deconstructs into a disordered flat phase. The (110) facets of Ag and Pd are candidates for realizations of preroughening. The preroughening transition is shown to be a line of continuously varying exponents using Coulomb-gas methods. Inside and outside corners of steps on the surface have different energy. The topological charge of this interaction is identified. It does not alter the roughening transition, but is relevant at the preroughening transition, and leads to generalized disordered flat phases.