Solid oxygen
Solid oxygen forms at normal atmospheric pressure at a temperature below 54.36 K (−218.79 °C, −361.82 °F). Solid oxygen O2, like liquid oxygen, is a clear substance with a light sky-blue color caused by absorption in the red part of the visible light spectrum.
Oxygen molecules have attracted attention because of the relationship between the molecular magnetization and crystal structures, electronic structures, and superconductivity. Oxygen is the only simple diatomic molecule (and one of the few molecules in general) to carry a magnetic moment. This makes solid oxygen particularly interesting, as it is considered a 'spin-controlled' crystal that displays antiferromagnetic magnetic order in the low temperature phases. For papers dealing with the magnetic properties of solid oxygen we refer to magnetisation of condensed oxygen under high pressures and in strong magnetic fields by R.J. Meier, C.J. Schinkel and A. de Visser, J. Phys. C15 (1982) 1015-1024, far infrared absorption dealing with the magnetic excitations or spinwaves in Meier R J, Colpa J H P and Sigg H 1984 J. Phys. C: Solid State Phys. 17 4501. At very high pressures, solid oxygen changes from an insulating to a metallic state; and at very low temperatures, it even transforms to a superconducting state. Structural investigations of solid oxygen began in the 1920s and, at present, six distinct crystallographic phases are established unambiguously.
The density of solid oxygen ranges from 21 cm3/mol in the α-phase, to 23.5 cm3/mol in the γ-phase.
A total of six different phases of solid oxygen are known to exist:
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