Melting transition of two-dimensional crystals

Abstract

The solíd-liquíd phase transítíon (PT) in two-dímensional crystals is studied under the assumption that it ís driven by the díssocíation of elastic dípoles. It ís shown that thís PT ís of tirst-order and corresponds to a díssocíatíon transítion of elastic dipoles. For systems where, via thermal nucleation metastable polycrystalline states are possible besides elastic-dipole formation, a more-complex phase díagram is postulated with !ines of tirst- and second-order PT. In the light of these concepts molecular-dynamics experiments with long- and short-range interactions in two and three dimensions are discussed. Solid-liquid PT observed in various experimental monolayer systems and showing tirst- and second-order PT are interpreted in terms of the theory developed.