First-principles prediction of new gas hydrates

Gas hydrates can form under low temperature and high pressure (~kbars) conditions and as a result occur naturally on Earth and within the solar system. They have applications in industry in storage and transport of gases. We explore computationally the stability of new gas hydrates, with a focus on the chiral water network S_χ, the metastable ice structure ice XVII, associated with the C₀ hydrogen hydrate and the CO₂ HP-hydrate [1]. S_χ has been shown experimentally to be readily emptied [2]. Computationally, S_χ has been shown to form at least metastable hydrates with He, Ne and Ar [3]. Here we present a density functional theory (DFT) study of molecular N₂ and O₂ gas hydrates based on filled S_χ, and analyse the phase evolution in the ground state, which shows a strong dependance on pressure and filling ratio. O₂ gas hydrate has the curious potential to form a magnetically ordered structure.

[1] D. M. Amoset al., J. Phys. Chem. Lett., vol. 8, no. 17, pp. 4295–4299, 2017.
[2] Del Rosso L, Celli M, Ulivi L (2016), Nat Commun 7:13394.
[3] P. Teeratchanan and A. Hermann, J. Chem. Phys., vol. 143, no. 15, 2015.