Scientists at the University of Edinburg, UK and at the National Instutute of Advanced Industrial Science and Technology in Tsukuba, Japan have discovered the crystal structure of solid red oxygen that forms at high pressures.
From Nature.com:
As a gas, oxygen molecules (O2) normally float around with only passing attraction to each other. But increasing pressure forces the molecules together, turning oxygen into first a magnetic, pale blue liquid, then a pale blue solid at 54,000 times atmospheric pressure (5.4 GPa).
In 1979, chemists discovered that, at pressures above 10 GPa, oxygen becomes a red solid. At 96 GPa, oxygen molecules are so close that electrons flow freely between them, in a metallic phase seen in 1990.
Instead, it appears that oxygen gangs up under pressure into groups of four pairs, in a shape like a squashed cube. These clumps of four O2 molecules could also be called a single O8 molecule — but they aren’t in a ring. The result demands a rethink of theoretical calculations about the behaviour of dense oxygen.
Exciting as it is, solid red oxygen seems, for the moment, useless. It is made in tiny amounts and vaporizes as soon as the pressure lifts. Nor will it be found in nature: despite the high pressures found in places such as inside the Earth, non-gaseous oxygen almost always joins to other elements, as an oxide or in water.
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