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 particlesinteracting through a Lennard-Jones pairwise potential is performed at fixedtemperature and vanishing external pressure. As the temperature is increased, asolid-to-liquid transition occurs. When the melting temperature $T_c$ isapproached from below, there is a proliferation of dislocation pairs and theelastic constant approaches the value predicted by the KTHNY theory. Inaddition, as $T_c$ is approached from above, the relaxation time increases,consistent with an approach to criticality. However, simulations fail toproduce a stable hexatic phase using systems with up to 90,000 particles. Asignificant jump in enthalpy at $T_c$ is observed, consistent with either afirst order or a continuous transition. The role of external pressure isdiscussed.