Characterization of the melting transition in two dimensions at vanishing external pressure using molecular dynamics simulations

摘要

A molecular dynamics study of a two-dimensional system of particles interacting through a Lennard-Jones pairwise potential is performed at a fixed temperature and vanishing external pressure. As the temperature is increased, a solid-to-liquid transition occurs. When the melting temperature T_c is approached from below, there is a proliferation of dislocation pairs and the elastic constant approaches the value predicted by the KTHNY theory. In addition, as T_c is approached from above, the relaxation time increases, consistent with an approach to criticality. However, simulations fail to produce a stable hexatic phase using systems with up to 90,000 particles. A significant jump in enthalpy at T_c is observed, consistent with either a first order or a continuous transition. The role of external pressure is discussed.