Predicting the Liquid-Vapor Critical Point from the Crystal Anharmonicity

A “universal” dependence is predicted of the reduced critical parameters, k_BT_c / E₀(γ), V_c / V₀(γ), and P_cV_c/k_BT_c  =  Z_c(γ), on the crystal anharmonicity γ (closely related to the Grüneisen parameter Γ_G). It is based on a simplified embedded-atom type approach which enables one to utilize the universal zero-temperature equation of state in a version of fluid perturbation theory. This model's critical temperature and density agree with the experimental results for both the heavy rare gases ( γ≃2.85) and heavy alkali metals ( γ≃1.35). Predicted critical parameters for many other liquid metals are consistent with previous estimates, but the model is not applicable when directional bonding is important.