Molecular Dynamics Study of Orientation and Thermal Motion of Guest Molecules in Large Cage of Structure II Hydrate

Abstract

We propose using hydrates as a distinct chemical reaction field apart from the normal gas and liquid phases. The molecular dynamics of bulk structure II hydrates were explored to better understand the position and behavior of the guest molecules in the hydrate, which influences the hydrate's reaction processes. The location and rotational motion of the guest molecules in the cage were explored using the projection positions of the atoms on the cage faces to which the atoms were orientated. The hydrogen atoms radially connected to the six-membered ring and the center of the cage’s circumferential faces acted together to constrain the benzene and cyclohexane molecules. Cyclopentane and tetrahydrofuran molecules were less restricted because the number of hydrogen atoms radially bound to the five-membered ring did not correspond to the number of circumferential faces. Tetrahydrofuran rotated in the cage, with oxygen atoms aligned more strongly on the pentagonal faces than the hexagonal faces.