Theoretical modeling of the thermodynamic properties and the phase diagram of binary gas hydrates of argon and hydrogen

Theoretical calculation of the thermodynamic properties and determining of equilibrium hydrate composition of binary argon + hydrogen hydrates has been performed with taking into account the concurrent cage occupation by different guest types. For this purpose the original previously developed approach has been used that allows to take into account multiple cage occupancy and the possibility of mixed clusters inside the cages as well as the influence of guest molecules on the host lattice. Separately, argon and hydrogen form cubic structure II (sII) hydrates. Therefore, in this work we considered only sII gas hydrates formation. It is shown that thermodynamic stability of binary argon + hydrogen hydrates strongly depends on the presence of argon in the gas phase as the heavier component. Thus, with increasing argon content in the system the hydrate stability field extends to low pressures with increase of argon fraction in the small cavities.