A Simple Theory of Melting and Condensation in Two-Dimensional System

概要

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Solid-liquid-gas phase transition is studied, using a simple two-dimensional model proposed by Collins. It is a simplified Bernal lattice which contains equilateral triangles and squares. Some lattice sites would be vacant, representing holes. An interatomic potential has a hard core repulsion and a short range attraction. Two kinds of order parameters are introduced to describe disorder of the system. One is related to the Bernal structure and plays a role at the solid-liquid-transition. The other is related to the hole density and plays a role at the liquid-gas transition. We get a phase diagram which has the three phase including a triple point and a critical point. The temperature of the triple point and the critical point is located at k_BT_t/ε≃ 0.81 and k_BT_c/ε≃1.27, respectively, where ε is the depth of an attractive potential. The density change and the latent heat are calculated along each transition line. The obtained results are quite analogous to the behavior of usual three-dimensional substances.
理論物理学刊行会の論文
1980-01-25