Theoretical Characterization of the High Pressure Nonclathrate CO2 Hydrate

Abstract

On the basis of results from exhaustive first-principles simulations, we report a thorough description of the recently identified high pressure phase of the CO2 hydrate, and provide an estimation of the transition pressure from the sI low pressure phase to the C-0 high pressure (HP) phase around 0.6 GPa. The vibrational properties calculated here for the first time might be useful to detect this HP structure in extraterrestrial environments, such as the Jupiter ice moons. Interestingly, we also find that CO2 gas molecules are quasi-free to diffuse along the helical channels of the structure, thus allowing the interchange of volatiles across a solid icy barrier. Taking into account its density and comparing it with other substances, we can estimate the naturally occurring zone of this CO2@H2O HP phase within a giant ice moon such as Ganymede. Other potential planetary implications that all of the found properties of this hydrate might have are also discussed.