Methane hydrate clathrates: effects in the simulation of melting arising from the assumption of simple combining rules in interatomic potentials

ABSTRACT

We discuss how the use of the conventional Lorentz–Bertholet mixing rules for the Lennard–Jones potentials for water and methane in simulations of their mixture in the methane hydrate clathrates underestimates the strength of the methane–water interaction due to the fact that the electrostatic interactions in the water model are not transferred to the methane–water interaction. We compare the results of standard models in which we artificially enhance the methane–water interaction above that given by the mixing rules. We compare with a new model developed based on ab initio calculations without using mixing rules and find that there is better agreement in the behaviour of melting clahtrate when the interaction is enhanced. We also introduce a software tool created for this work for creating ice configurations with orientational disorder but consistency with the Bernal–Fowler ice rules. The paper begins with a personal perspective on the role of the molecular dynamics code DL_POLY in ongoing materials research.

KEYWORDS:

• Methane hydrate clathrate
• combining rules
• molecular dynamics simulations
• DL_POLY
• water

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Queen Mary, University of London.