Characterization of the Melting Transition in Two Dimensions at   Vanishing External Pressure Using Molecular Dynamics Simulations
  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 $T_c$ 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. 
Daniel Asenjo, Fernando Lund, Sim\'on Poblete, Rodrigo Soto and Marcos   Sotomayor
cond-mat.stat-mech cond-mat.mtrl-sci