Crystal structure of the high-pressure monoclinic phase-II of cristobalite, SiO2

The crystal structure of the high-pressure phase-II of cristobalite has been solved by neutron diffraction (space group P2(1)/c, a = 8.3780(11) Angstrom, b = 4.6018(6) Angstrom, c = 9.0568(13) Angstrom, beta = 124.949(7)degrees, at P = 3.5 GPa). This phase corresponds to a distortion of the high-temperature cubic beta-phase, rather than of the ambient temperature and pressure tetragonal alpha-phase.