Monte Carlo and molecular dynamics simulations were carried out to determine whether stable methane

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Monte Carlo and molecular dynamics simulations
were carried out to determine whether stable
methane clathrates could in principle form in the
interlayers of hydrated Na-montmorillonite in
equilibrium with seawater under ambient
conditions. Stable interlayer methane clathrate
structure were found to occur under pressures as
low as 10 atm and at temperatures as high as 300
K in simulations of a three-layer hydrate of
Na-montmorillonite containing 0.5 CH4 per clay
mineral unit cell. On the basis of these
simulations, methane hydrate is proposed to occur
in natural sediments with a portion of clay
mineral surface actively involved in promoting
clathrate formation. Figure shows the snapshot
after 3,200,000 steps of Monte Carlo simulations
for 0.5 CH4 per unit cell system. The red spheres
represent mineral O, the gray spheres represent
mineral Si, and the pink spheres represent Al in
tetrahedral charge substitution sites in place of
Si and Al in octahedral layer. Water O are blue
and H are white, while N are purple and methane
molecules are orange. (Original figure created
by Dr. Sung-Ho Park and modified from Park,
S.-H. and Sposito, G., J. Phys. Chem. B. 2003,
107, 2281-2290)