Ice IV

Ice IV was discovered by the Nobel prize winner Percy Williams Bridgman in 1935 (Ref. 1). Ice IV is metastable, having no region of stability in the ice phase diagram. Ice IV is proton disordered and is a member of the $R{\overline {3}}c$ space group, having 16 molecules per unit cell. Its structure was resolved by Hermann Engelhardt and Barclay Kamb in 1981 (Ref. 2).

References

1. P. W. Bridgman "The Pressure-Volume-Temperature Relations of the Liquid, and the Phase Diagram of Heavy Water", Journal of Chemical Physics 3 pp. 597-605 (1935)
2. Hermann Engelhardt and Barclay Kamb "Structure of ice IV, a metastable high-pressure phase", Journal of Chemical Physics 75 pp. 5887-5899 (1981)
3. C.G. Salzmann, I. Kohl, T. Loerting, E. Mayer, and A. Hallbrucker "Pure ices IV and XII from high-density amorphous ice", Canadian Journal of Physics 81 pp. 25-32 (2003)