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Thermochemistry of strontium incorporation in aragonite from atomistic simulations

Ruiz Hernandez, Sergio, Grau-Crespo, Ricardo, Ruiz-Salvador, A. Rabdel and de Leeuw, Nora 2010. Thermochemistry of strontium incorporation in aragonite from atomistic simulations. Geochimica et Cosmochimica Acta 74 (4) , pp. 1320-1328. 10.1016/j.gca.2009.10.049

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We have investigated the thermodynamics of mixing between aragonite (orthorhombic CaCO3) and strontianite (SrCO3). In agreement with experiment, our simulations predict that there is a miscibility gap between the two solids at ambient conditions. All SrxCa1−xCO3 solids with compositions 0.12 < x < 0.87 are metastable with respect to separation into a Ca-rich and a Sr-rich phase. The concentration of Sr in coral aragonites (x ∼ 0.01) lies in the miscibility region of the phase diagram, and therefore formation of separated Sr-rich phases in coral aragonites is not thermodynamically favorable. The miscibility gap disappears at around 380 K. The enthalpy of mixing, which is positive and nearly symmetric with respect to x = 0.5, is the dominant contribution to the excess free energy, while the vibrational and configurational entropic contributions are small and of opposite sign. We provide a detailed comparison of our simulation results with available experimental data.

Item Type: Article
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Publisher: Elsevier
ISSN: 0016-7037
Last Modified: 05 Nov 2019 03:48

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