Ice IX is a metastable form of solid water that exists at temperatures below 140K and pressures between 200 and 400 MPa. It has a tetragonal crystal lattice and a density of 1.16 g/cm³, slightly higher than ordinary ice.

Ordinary water ice is known as Ice-I (in the Bridgman nomenclature). Different types of ice, from ice-II to ice-XII have been created in the laboratory at different temperatures and pressures.

Ice IX is not to be confused with "Ice-9" (a fictional discovery in the novel Cat's Cradle by Kurt Vonnegut).

References

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Bridgman, P. W. (1937) J. Chem. Phys. 5, 964.

External References

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• London South Bank University Report

Forms of water | Water ice