Bromate incorporation in calcite and aragonite

The presence of bromine as a trace-element in calcium carbonate speleothems constitutes useful proxy past volcanic activity, thus helping to provide input parameters for climate model simulations and risk assessment. However, the chemical nature bromine-containing impurities phases forming is not understood, which limits interpretation experimental measurements on speleothems. We present here computer simulation study, based quantum mechanical calculations, incorporation BrO 3 − oxyanions CaCO polymorphs calcite aragonite. discuss how relative distributions bromate charge-compensating alkali-metal cations are determined by interplay between an impurity binding effect (which stronger aragonite than calcite, changes order Li < Na K) configurational entropic that tends disassociate impurities. For concentrations above parts-per-million, can be expected paired, nearest-neighbour configurations, with compensating cations. Bromate substitution, compensated sodium or potassium cations, predicted metastable respect phase separation solid NaBrO KBrO phases, respectively, but solubility still higher those calculated tetrahedral (SO 4 ) 2− (MoO used alternative records