Thermal Expansion Coefficient of sI Clathrate Hydrates by Molecular Dynamics Simulation

We perform molecular dynamics simulations for the structure I (sI) clathrate hydrates of linear molecules Acetylene (C2H2), Carbon disulfide (CS2) and Carbonyl sulfide (OCS) under a wide range of pressure and temperature conditions. Systems studied include sI binary clathrate hydrates of C2H2 (large 14-sided cage, L) + CH4 (small 12-sided cage, S), CS2 (L) + CH4 (S) and OCS (L) + CH4 (S). The simulations were started with guest molecules positioned at the cage center of the hydrate. Two water models, the SPC/E and TIP4P/ice, were used in the simulations. We focus on the calculation of the lattice parameters of the three hydrates and their dependence on temperature. The slope of the lattice parameters against temperature use to calculation isobaric thermal expansion.