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Thermochemistry of strontium incorporation in aragonite from atomistic simulations

Ruiz-Hernandez, SE; Grau-Crespo, R; Ruiz-Salvador, AR; De Leeuw, NH; (2010) Thermochemistry of strontium incorporation in aragonite from atomistic simulations. GEOCHIM COSMOCHIM AC , 74 (4) 1320 - 1328. 10.1016/j.gca.2009.10.049.

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Abstract

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 similar to 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. (C) 2009 Elsevier Ltd. All rights reserved.

Type:Article
Title:Thermochemistry of strontium incorporation in aragonite from atomistic simulations
DOI:10.1016/j.gca.2009.10.049
Keywords:MOLECULAR-DYNAMICS SIMULATIONS, FREE-ENERGY MINIMIZATION, SOLID-SOLUTIONS, SR COORDINATION, CORAL ARAGONITE, THERMODYNAMIC PROPERTIES, CALCITE, GROWTH, TEMPERATURE, CACO3
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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