The full structure of the high-pressure cubic phase I' of hydrogen sulfide
has been solved using neutron diffraction data. The molecules are partially
rotationally disordered about the [111] axes, as in phase II at ambient pr
essure but with markedly greater nonuniformity of thr toroidal D distributi
on. The changes in structure at the II --> I' transition signal the onset o
f significant pressure-induced hydrogen bonding.