De Leeuw, NH;
Thermochemistry of strontium incorporation in aragonite from atomistic simulations.
GEOCHIM COSMOCHIM AC
1320 - 1328.
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.
|Title:||Thermochemistry of strontium incorporation in aragonite from atomistic simulations|
|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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