A method distinguishing between guest molecules that can form sI, sII, and sH hydrogen clathrates

Abstract

A new method based on free energy calculations is proposed for discriminating between promoters that can form sI, sII, and sH hydrogen clathrates. The method is validated by comparing results of this computational approach to known experimental data reporting which type of clathrate structure is formed with the help of a particular promoter molecule. Good agreement is found. The free energy results confirm a well-known simple rule of thumb based on the van der Waals volume of the promoter molecules to distinguish between potential sH or sII hydrate formers. The method predicts an unusually strong temperature dependence of the stability of hydrogen clathrate hydrates for some hitherto untested promoter molecules, which can be exploited if easy release of hydrogen is required.

Electric-Field Control of Neon Uptake and Release to and from Clathrate Hydrates

“…The Helmholtz or Gibbs free energy dictates the stability of a system under a canonical ( NVT ) ensemble or isothermal–isobaric ensemble ( NPT ), respectively. Free-energy calculation of guest substitution in hydrates have been reported by MD. − Wierzchowski and Monson calculated the methane-filling free energy calculation of sI clathrate, using Monte Carlo simulation . In any event, the kinetics of these cage-filling/emptying transitions may be influenced by free-energy considerations, from a transition-state-theory perspective.…”