Equation of state for solid solution–liquid–vapor equilibria at cryogenic conditions

An equation of state (EOS) that can represent solid–liquid, solid–vapor, and solid–liquid–vapor equilibria at planetary cryogenic conditions is presented. The EOS consists of two parts that are based on a common framework of the Thermodynamic Perturbation Theory: the fluid part that applies the Perturbed-Chain Statistical Associating Fluid Theory, and the solid part that applies the Lennard–Jones solid EOS. Our compelling results of the multiphase equilibria of chemical species and their mixtures encourage further development of the EOS to become a powerful tool in scientific investigations on objects in the outer-planet region.