Low barriers for hydrogen diffusion in sII clathrate

Abstract

The transport of gas molecules in hydrates is presently poorly understood. In sII structured hydrates with hydrogen guests there is, for instance, a mismatch between experimental and computed values for diffusion constants. We provide an explanation for the experimentally observed diffusion rates, using DFT-based molecular dynamics simulations at 100 K. By considering the effect of cage occupancy, as well as the flexibility of the water lattice, we show that barriers for hydrogen diffusing between cages, can approach values as low as 5 kJ mol⁻¹, which is very close to experimental values.