Electrodissociation of clathrate-like structures

Abstract

In the present work, we develop molecular dynamics (MD) simulations in the NPT (isobaric–isothermic) ensemble to analyse the effect of an external electrostatic field over a cubic methane hydrate crystallite. The amplitude of the field is in the range 0.5–3.0 V/nm. For the simulations, we used the SPC/E rigid water model and a single-site model for methane at a temperature of 248 K and a pressure of 20 bar. When the external electrostatic field is applied, the water dipoles are oriented in such a way that the methane molecules can diffuse far away from the water cages, hence the clathrate dissociation takes place. This last phenomenon was observed for intensities above 1.5 V/nm. Taking the final configuration of each run as input, we develop a new set of MD simulations, and we observe that the stable clathrate is not recovered immediately when the external electrostatic field is turned off due to limitations in the simulation time.

Keywords:

• methane hydrates
• external electric field
• molecular simulation
• coordination number
• radial distribution function

PACS::

• 31.15.xv
• 36.40.Ei
• 36.40.Sx

Acknowledgements

D.P.L. thanks CONACYT for the financial support through a postgraduate scholarship. J.L.L. and M.M. thank the UAEM for the financial support under Grants 2625/2008U and 2263/2006, respectively. The authors thank Fernando Bresme for helpful discussions and Lorena Romero for the critical reading of the manuscript. Finally, the authors acknowledge the Laboratorio de Supercomputo in FC-UAEM for the technical support.