On the thermodynamic stability of clathrate hydrates IV: Double occupancy of cages

We have extended the van der Waals and Platteeuw theory to treat multiple occupancy of a single cage of clathrate hydrates, which has not been taken into account in the original theory but has been experimentally confirmed as a real entity. We propose a simple way to calculate the free energy of multiple cage occupancy and apply it to argon clathrate structure II in which a larger cage can be occupied by two argon atoms. The chemical potential of argon is calculated treating it as an imperfect gas, which is crucial to predict accurate pressure dependence of double occupancy expected at high pressure. It is found that double occupancy dominates over single occupancy when the guest pressure in equilibrium with the clathrate hydrate exceeds 270 MPa. (C) 2004 American Institute of Physics.

Digital Object Identifer:10.1063/1.1782471
Published with permission from the copyright holder. This is the institute's copy, as published in the Journal of Chemical Physics, Sep 2004, Volume 121, Issue 11, Pages 5488-5493.
Publisher URL:http://dx.doi.org/10.1063/1.1782471
Direct access to Thomson Web of Science record
Copyright © 2004 American Institute of Physics