Molecular dynamics simulations of structure-H hydrates formed with methane and 3,3-dimethylpentane or 2,2-dimethylpentane

Molecular dynamics (MD) simulations of structure-H hydrates formed with methane +2,2-dimethylpentane and methane +3,3-dimethylpentane were performed in the NPT ensemble. We obtained the trajectories and the distribution profile of the sites of the dimethylpentane molecules. The results revealed the distinct molecular motions of the two dimethylpentanes in the cages of the hydrates. The dimethylbutane molecules mainly exhibited translational motion, but rotational motions were also observed. Despite the similar molecular structure of the two dimethylpentanes, distinct molecular motions were observed; a greater spacial range of molecular motions was observed with 2,2-dimethylpentane. The difference in the unit cell sizes of the hydrates, which were relevant to the different molecular motions, was also observed.