Fig. 2
From: Electrostatic force driven helium insertion into ammonia and water crystals under pressure

Structures of corresponding compounds under high pressure. NH3 structures in space group of a Pma2 under 150 GPa, b P21/m under 350 GPa, c Pnma at 600 GPa. d NH3He structure in space group of P212121 under 600 GPa. e H2O structure in space group of Pbcm under 400 GPa. f (H2O)2He structure in space group of Ibam under 400 GPa. The blue and red balls represent N and O atoms; the small and large white balls represent the H and the He atoms