Communication: Structural interconversions between principal clathrate hydrate structures

Abstract

Gas clathrate hydrates formed with most gases belong to three common and well characterized crystalline structures known as sI, sII, and sH, although molecular mechanisms for their structural interconversions have remained poorly understood. Here, we present potential mechanisms for the interconversions between sI and sH and sII and sH, as observed within molecular simulations of the cross-nucleation of different methane hydrate phases. We find that a 4151062 cage intermediates the structural interconversion between sI and sH, while a sII crystal can form on a sH template directly. These structural interconversion pathways emphasize the diversity of possible clathrate hydrate phases characterized by a variety of tetrahedrally hydrogen-bonded structures.