The vibrational signatures of the calcium oxalate polyhydrates are investigated using a combination of Density Functional Theory‐Dispersion corrected, Fourier Transform‐ Raman and ‐Infrared (IR) spectroscopies. Most vibrational bands were assigned and the theoretical predictions were compared with in‐house and other experimental data, for both, IR and Raman spectroscopies. Such an approach allowed a more accurate analysis of vibrational spectra helping in the completion of the band assignments of the vibrational bands of the mono, di, and tri hydrate calcium oxalate (COM, COD, and COT). Particular attention has been paid to the degree of hydration of COD, the low Raman wavenumbers, and the presence of oxalic acid in natural calcium oxalate polyhydrates. The obtained results are expected to be supportive in the detection of the different polyhydrates in natural samples, such as in kidney stones.

Monohydrated and dihydrated calcium oxalate have been widely studied in the literature because of their role in urolithiasis, a mammal pathology responsible for the formation of stones in the kidney. It is clear that the physicochemical environment plays a crucial role in the crystal growth and the resulting morphologies of calcium oxalates. To study these processes, reliable models for the calcium oxalate's faces, exposed to water and potential additives, are needed.Here, we have used a total surface energy minimization approach to predict the crystal morphology of the calcium oxalate monohydrate and dihydrate phases. Surface energies were calculated at density functional theory level, taking into account surface relaxation and the effect of solvation. An excellent agreement was found between theoretically predicted morphologies and their experimental counterparts obtained by SEM, clearly demonstrating the importance of the inclusion of water in the model for the prediction of morphologies.