Nonanalytical equation of state of the hard sphere fluid

A model based on classical nucleation theory is proposed to describe phase behavior in stable and metastable regions near a first-order phase transition. The resulting equation of state is not an analytical function at the phase transition point. The model is tested on the hard sphere fluid where it is combined with the virial expansion at low densities. This nonanalytical equation of state is able to capture the observed anomalous increase of pressure at high densities. Consequences to description of phase equilibria by classical equations of state are discussed.