A phase-field model for liquid-vapor transitions induced by temperature and pressure

We scrutinize the equations ruling the liquid-vapor phase transition. Starting from the macroscopic state equations of the vapor and the liquid pure phases, we propose a phase-field model which is thermodynamically consistent and accounts for both temperature and pressure variations during the evaporation process. In particular, we are able to determine the explicit expression of the Gibbs free enthalpy. As a consequence, the Clausius-Clapeyron formula is obtained and the customary form of the vapor pressure curve is recovered.