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.

Different force fields for the graphene–CH4 system are proposed including pseudo-atom and full atomistic models.

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The interaction of CO with graphene was studied at different theoretical levels. Quantum-mechanical calculations on finite graphene models with the use of coronene for coupled cluster calculations and circumcoronene for B97D calculations showed that there was no preferential site for adsorption and that the most important factor was the orientation of CO relative to graphene. The parallel orientation was preferred, with binding energies around 9 kJ mol at the CCSD(T) and B97D levels, which was in good agreement with experimental findings. From a large number of CO-circumcoronene and CO-CO interactions, computed at different distances and randomly generated orientations, parameters were fit to the improved Lennard-Jones potential. Such potentials, together with others describing the intramolecular dynamics of graphene, were subsequently employed in classical molecular-dynamics simulations of the adsorption of CO on graphene by using the canonical ensemble. The obtained results showed that the introduction of flexibility in graphene, which simulated the effects associated to curvature of the surface, diminished the adsorption level and that, as expected, adsorption also diminished with temperature.