Crystal structure of bent carbon dioxide phase IV

The crystal structure of carbon dioxide phase IV (CO2-IV) has been characterized based on powder angle-resolved x-ray diffraction data obtained in situ at 300-750 K and 11-50 GPa. The results confirm that in this high-pressure polymorph O=C=O molecules are nonlinear. Rietveld analyses of the x-ray data yield two plausible structures: P4(1)2(1)2 (alpha-SiO2 cristobalite) and Pbcn (alpha-PbO2, post-stishovite). Carbon dioxide molecules are bent slightly more in the Pbcn phase (