Energy and spectral characteristics of hydrogen occupied pure and tetrahydrofuran doped water cages

Abstract

Hydrogen clathrate hydrates consist of hydrogen molecules which can be encapsulated in several polyhedral water cages. In this work, we apply quantum chemistry methods to calculate interaction energy, cage deformation energy and spectral properties with multiple occupancy of hydrogen in (H2O)20, and pure and tetrahydrofuran doped (H2O)28 water cages. The interaction energies and cage deformation energy show that H2@(H2O)20, 4H2@(H2O)28 and H2 + THF@(H2O)28 cages are more preferred compared to other occupancies. The vibrational modes of water molecules of the H2@(H2O)20, 4H2@(H2O)28 and H2 + THF@(H2O)28 cages show a red-shift relative to the 2H2@(H2O)20, (nH2)n=1–3@(H2O)28 and 2H2 + THF@(H2O)28 cages. The interaction energies and spectral trends validate experimental findings on maximum occupancy of hydrogen in various water cages.