Translation-rotation energy levels of one H2 molecule inside the small, medium and large cages of the structure H clathrate hydrate.

We report quantum dynamics calculations of the translation-rotation energy levels of one hydrogen molecule inside the small, medium and large cages of the structure H clathrate hydrate. The calculations are performed using the multiconfiguration time-dependent Hartree (MCTDH) method. Some low-lying states are computed for para-H(2), ortho-H(2), para-D(2), ortho-D(2) and HD, by block improved relaxation.