Cellular Automata Simulations of Vapor–Liquid Equilibria

Phase transitions and phase equilibria are among the most fundamental phenomena in the physical and environmental sciences. In the present work an asynchronous stochastic cellular automata model for the equilibrium between a liquid and its vapor is presented. The model is visual, dynamic, and employs just two rules—an attraction probability and a gravitational preference. Application of the attraction rule alone yields a ‘mist’ within the vapor, whereas application of the gravitational rule by itself yields an isothermal atmospheric profile. Application of both rules together causes the vapor to evolve to a liquid phase with a vapor phase above it. Introduction of a third rule for short-range attraction/repulsion more clearly resolves the liquid/vapor interface.