Characterization of the Melting Transition in Two Dimensions at Vanishing External Pressure Using Molecular Dynamics Simulations
Abstract
A molecular dynamics study of a two dimensional system of particles interacting through a Lennard-Jones pairwise potential is performed at fixed temperature and vanishing external pressure. As the temperature is increased, a solid-to-liquid transition occurs. When the melting temperature Tc 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 Tc 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 Tc is observed, consistent with either a first order or a continuous transition. The role of external pressure is discussed.