Extension of a van der Waals Equation of State to the Solid-liquid-vapor Phases of a Lennard-Jones System

An existing van der Waals (vdW) equation of state (EOS) based on hard-sphere repulsions during intermolecular interactions was extended to a Lennard-Jones (LJ) system. Specifically, an EOS for a perfect solid and liquid v5 (Y. Kataoka and Y. Yamada, J. Comput. Chem. Jpn.,12, 181–189 (2013)) was simplified to satisfy the Rigby conditions for a generalized vdW EOS. The phase diagram of argon was reproduced in pressure-temperature space using this extended EOS, and a phase diagram in temperature-density space was also generated and found to be qualitatively consistent with the LJ system.