Domain Walls and the Melting of Commensurate Surface Phases

Commensurate adsorbed surface phases, particularly p×1 rectangular and √3×√3 hexagonal phases, exhibit two (or more) classes of domain wall, reflecting a lower than ideal symmetry; these compete statistically and undergo wetting transitions. Scaling arguments and model calculations indicate that new types of continuous melting transitions, possibly already seen in Kr on graphite, can thereby arise.