The orientational disordered phase of crystalline oxygen

The first crystal structure formed by freezing molecular oxygen contains a lot of orientational disorder. Given the considerable interest in the solid phases of oxygen across both temperature and pressure, it is long overdue that the orientational disorder should be properly understood. Actually, whereas many simple molecular crystals have one molecule per lattice point, the unit cell of the disordered phase of oxygen has two distinct sites for the molecules of quite different symmetry. The best approach to understand orientational disorder in crystals is using a combination of neutron total scattering with analysis using the Reverse Monte Carlo method. This is what we propose here, giving us the first detailed understanding of orientational disorder in solid oxygen.