Massively parallel molecular dynamics simulation of formation of clathrate-hydrate precursors at planar water-methane interfaces: Insights into heterogeneous nucleation

Abstract

The formation of methane-hydrate precursors at large planar water-methane interfaces has been studied using massively parallel molecular dynamics in systems of varying size from around 10 000 to almost 7 × 10(6) molecules. This process took two distinct steps. First, the concentration of solvated methane clusters increases just inside the aqueous domain via slow diffusion from the methane-water interface, forming "clusters" of solvated methane molecules. Second, the re-ordering process of solvated methane and water molecules takes place in a manner very roughly consistent with the "blob" hypothesis, although with important differences, to form hydrate precursors, necessary for subsequent hydrate nucleation and crystallisation. It was found that larger system sizes serve to promote the formation rate of precursors.

Methane Clathrate Hydrate Nucleation Mechanism by Advanced Molecular Simulations

“…56 Finally, Vatamanu and Kusalik 22 have shown that local fluctuations of solute concentration beyond the equilibrium value might enhance nucleation. Analogous effects have also been observed in other clathrates (see, for example, ref 40).…”

Structural and dynamical properties of methane clathrate hydrates from molecular dynamics: Comparison of atomistic and more coarse-grained potential models

“…31,38 Despite the clear underlying limitations of such a 'coarse-grained' potential, such a simple model has a potentially clear and valuable contribution for hydrate simulation, and it has established their value for equilibrium simulation of methane hydrates 31 and methane-water interfaces. 39 In any event, re-parameterisng coarse-grained models such as mW and a single-particle variant of TIP5P to and mTIP4P/2005REM 40 may offer similar greater accuracy than commonly used atomistic models such as SPC/E at only a hundredth of the computational cost. 40 mW-type coarse grained models truncate after three body…”

Clathrate structure-type recognition: Application to hydrate nucleation and crystallisation

“…1,2 A unit cell in sII hydrate consists of 136 water molecules forming sixteen small 5 12 cages and eight large hexadecahedral 5 12 6 4 cages. 1,2 In recent years, the molecular simulation of clathrate hydrates has revealed much about their structural properties, 3 and Monte Carlo 4 and molecular dynamics (MD) simulations, whether brute force (i.e., standard) [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] or biased, [22][23][24][25] of hydrate formation have revealed a propensity for either (approximately) sI or sII polymorphs to form, despite one form typically being most thermodynamically stable for a given guest type (and temperature/pressure). Given that such simulation can provide molecular-level insights into hydrate-formation dynamics, this allows for probing the structural nature of the growing hydrate a) Authors to whom correspondence should be addressed.…”