Synthesis and Structure of Two New Cadmium Carbonates at Extreme Conditions

We synthesized CdC2O5and a new high-pressure polymorph of CdCO3by laser heating otavite, CdCO3, in CO2at 43 GPa. The structure of CdC2O5contains pyramidal [C4O10]4–building blocks formed by [CO4] tetrahedra, where the carbon is in 4-fold coordination. In addition, we found a new monoclinic (P21/c) high-pressure polymorph of CdCO3with trigonal [CO3]2–groups. Both new structures were characterized by single-crystal X-ray diffraction, Raman spectroscopy, and DFT calculations.