Crystal structures of (a) I4/mcm Xe₂F at 200 GPa. (b) P-6m2 XeCl₄ at 100 GPa. (c) R-3m XeN₆ at 150 GPa. (d) Pm-3m XeFe₃ at 250 GPa. (e) Pmmn XeNi₃ at 250 GPa. (f) P4/mmm LiAr at 160 GPa. (g) I4/mmm CsXe₂ at 200 GPa. (h) I4/mmm Mg₂Xe at 200 GPa. (i) Ibam (H₂O)₂He at 300 GPa. (j) Fd-3m He₂H₂O at 70 GPa. (k) Phase diagram of the helium-water system at high pressures. Adapted with permission from Ref. [111]. Copyright (2019) Nature.