Effect of potential energy on the formation of methane hydrate

Molecular dynamics (MD) simulations were performed on the system of methane and water using the SPC/TSE (TSE) and the optimised SPCE/OPLS-UA potentials to decide how the structural and dynamical properties of the methane hydrate are affected when adopting different potential energy models. Our simulations were carried out at a temperature range from 230 to 260 K and a pressure of 300 bar under NPT condition. The results that compare the two models were discussed in terms of the potential energy, hydrogen bond number, mean square displacement, diffusivity, radial distribution function and number density profile for the two models. Investigation over a timescale of 85 ns demonstrated that the methane–water interaction potential energy does have an effect on the structural and dynamical properties and consequently on the hydrate formation. For the optimised SPCE/OPLS-UA potential no methane hydrate was formed over a temperature range of 230–260 K, while for the TSE model the formation of methane hydrate was observed at 230 and 240 K. The hydrate formation is not favoured by the optimised SPCE/OPLS-UA model where the methane–water interaction potential energy becomes more attractive. However, the TSE model, the more repulsive methane–water potential, stabilizes the hydrate structure. Our results for the structural and dynamical properties are self-consistent.

Research Highlights► Understand the effect of the methane-water interaction potential on the methane hydrate formation. ► Hydrate formation is not favoured by the optimized SPCE/OPLS-UA model. ► TSE model, the more repulsive methane-water potential, stabilizes the hydrate structure.