First-principles path-integral based molecular dynamics simulation of hydrogen hydrate in C0 phase

The crystal structure proposed experimentally for C-0 phase of H-2 hydrate has been assessed by first-principles path-integral based molecular dynamics simulations. Our constant pressure and temperature simulations in the NPT ensemble suggest that H-2 hydrate in C-0 phase has a hexagonal unit cell in agreement with experiments. The fractional coordinates of H2O molecules also agree well with the experimental ones, supporting the presence of interpenetrating spiral chains of H-bonded water molecules. Limitations in the linear response theory used to compute the Raman spectra allow at least for a qualitative agreement with the observed experimental ones.