Computational investigation of the influence of tetrahedral oxoanions (sulphate, selenate and chromate) on the stability of calcium carbonate polymorphs

摘要: The incorporation of tetrahedral AO42− groups (A = S, Cr, Se) in CaCO3 polymorphs (calcite, aragonite and vaterite) is investigated from first principles calculations at the Density Functional Theory (DFT) level. We found that less dense softer vaterite crystal structure has greater capability to distort accommodating ions. calculated mixing enthalpies 0 K Ca(CO3)1−x(AO4)x Se, Cr) calcite are below 3 kJ mol−1 when x < 0.05, confirming small concentrations thermodynamically feasible these moderate temperatures. Calcite identified as most stable polymorph any dopant concentration (0 0.25). Although our results do not predict stability crossovers resulting group into polymorphs, they strongly support a reduction driving force for transformation AO4-bearing calcite.