Application of a Modified van Der Waals Model to Calculate Phase Diagrams of Binary Mixtures of Helium, Neon, Hydrogen, and Deuterium

Based on the previously developed modified van der Waals model for individual substances, updated thermal equations of state for helium, neon, hydrogen, and deuterium up to pressures of ~200 MPa and temperatures of ~1000 K are constructed, consistent with the experimental data on isothermal compression with an accuracy of ~1% in density (except for the region near the critical point). Their advantage lies in the relatively small (five) number of free parameters. Using these equations on the basis of a modified van der Waals model for mixtures, the phase diagrams of binary mixtures of helium, neon, hydrogen, and deuterium with each other and some other substances (argon, methane, hydrogen dioxide, etc.) are described. Using one additional parameter, satisfactory agreement with the liquid–gas phase equilibrium experiment is achieved for most of the named mixtures up to pressures of ~200 MPa. The developed approach can be used to describe phase diagrams of binary mixtures other than those considered.