Structural studies of β-O₂ under pressure

The structure and lattice compression of the β-O₂ phase have been studied by synchrotron x-ray diffraction experiments at 277 and 300 K. The pressure dependence of the lattice constants, a and c, obtained from a powder indicated anisotropic compressibility. a is almost three times as compressible as c. This large linear compressibility of a may be attributed to the antiferromagnetic interaction in the basal plane. Single-crystal analyses at 6.1 GPa and 300 K suggested that the oxygen atom is disordered with a threefold axis of symmetry.