Multicanonical Monte Carlo Calculation of the First-order Phase Transition of Lennard-Jones Fluids

The liquid-solid phase transition was investigated by the multicanonical Monte Carlo method for a bulk Lennard-Jones fluid system that consists of 256 argon particles. The reliability of the multicanonical weight factor we determined was confirmed by the flatness of the histogram obtained by the multicanonical Monte Carlo production run. The first-order phase transition between solid and liquid phase was observed around 130 K from the change in thermodynamic properties as a function of temperature. Besides, the small change between two solid structures was also observed at 60 K from the radial distribution function, from the heat capacity and from conventional canonical Monte Carlo calculation at 60 K. Neither of them is not f. c. c. structure which is known as the most stable

Thermodynamics of two lattice ice models in three dimensions

In a recent paper we introduced two Potts-like models in three dimensions, which share the following properties: (A) One of the ice rules is always fulfilled (in particular also at infinite temperature). (B) Both ice rules hold for groundstate configurations. This allowed for an efficient calculation of the residual entropy of ice I (ordinary ice) by means of multicanonical simulations. Here we present the thermodynamics of these models. Despite their similarities with Potts models, no sign of a disorder-order phase transition is found.Comment: 5 pages, 7 figure