UNIAXIAL INCOMMENSURATE RARE-GAS-MONOLAYER SOLIDS .1. STRUCTURE AND STATISTICAL-MECHANICS

Calculations are reported for uniaxial incommensurate solid phases of rare-gas monolayers adsorbed on triangular substrate surfaces. The monolayer is treated in a two-dimensional approximation with adatom-adatom pair potentials and a periodic adatom-substrate corrugation potential. The two signs of the substrate corrugation amplitude lead to solutions with different diffraction signatures. Structures are determined in the zero-temperature classical approximation and energies are calculated in the classical and quasiharmonic approximations. The energy of a domain wall is calculated as a function of temperature and the phase transition between commensurate and incommensurate lattices is treated. The in-plane motion of the domain walls is analyzed in terms of the Peierls barrier energy and the frequency spectrum of the monolayer for wave vectors in the direction of the misfit.