Molecular dynamics study of liquid-solid transition of dense lennard-jones liquid

We report a molecular dynamics simulation of solid-liquid phase transition. The system consists of 864 particles interacting with Lennard-Jones potential in N, E, V ensemble. A thermodynamic construction based on Helmholtz free energy surface is analysed and applied to the simulation data. It is shown that metastability limits can be obtained in this approach of simulation and a van der Waals type of loop in an E (internal energy) against 1/T plot can be used to construct an equal-area plot to locate the melting temperature. The thermodynamic properties of the liquid and solid branches can be thus connected. We use a Voronoi cell construction to present the configuration disorder of melting phenomenon from simulation data. Information entropy based on the distribution of Voronoi cell size and shape is calculated and compared with thermodynamic entropy of melting; the agreement is good. It is shown that instability associated with melting transition is mainly caused by change of shape of the cage volume in defect formation. Results of Voronoi analysis is consistent with the vacancy split-interstitial pair defect mechanism.