Anhydrous cadmium oxalate polymorphism: a first principle study†
The structure and properties of the β and of the recently discovered γ phases of anhydrous cadmium oxalate are here computed using a hybrid Hartree–Fock/density functional theory approach. The experimental data available for these phases are limited and in good agreement with the corresponding computed properties. Their infrared, reflectance and Raman spectra are computed and reference data for their dielectric and elastic properties are provided. Several configurations for the γ phase, resulting from partial occupancy of one oxalate site proposed in a recent investigation, are analysed and the structure re-defined; the final proposed configuration has no partial occupancy and exhibits an X-ray diffraction pattern that fully overlaps with that experimentally measured. A comparison with the properties of the stable trihydrated hydromorph is also provided. Since the structure of CdC2O4 is sensitive to its synthesis path, the data presented in this study will provide guidance in future characterisations of the synthesis products.