Gas clathrate hydrates are crystalline inclusion compounds formed when water and gas come into contact at high pressures and low temperatures. To date there are only three common gas hydrate structures, known as structures I, II and H. In contrast our recent computer simulations (Walsh et al., Science) show that several different types of gas hydrate cages and structures may be possible, in addition to the sI, sII, sH structures. Recently a new phase of a hydrogen hydrate has been discovered (Strobel et al., 2012), indicating the possibility of stabilizing new clathrate hydrate structures at very high pressures. The key objective of this proposal is to solve the structure of this new hydrogen clathrate hydrate phase using neutron powder diffraction.