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Issue 24, 2008
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Subsolidus phase relations in Ca2Mo2O8–NaEuMo2O8-powellite solid solution predicted from static lattice energy calculations and Monte Carlo simulations

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Abstract

Thermodynamic mixing properties and subsolidus phase relations of Ca2Mo2O8–NaEuMo2O8 powellites were modelled in the temperature range of 423–1773 K with static lattice energy calculations based on empirically constrained interatomic potentials. Relaxed static lattice energies (SLE) of a large set of randomly varied structures in a 4 × 4 × 2 supercell of I41/a powellite (a = 5.226 Å, c = 11.433 Å) containing 128 exchangeable (Ca, Na and Eu) atoms were calculated using the general utility lattice program (GULP). These energies were cluster expanded in the basis set of 69 pair-wise effective interactions and three configuration-independent parameters. Temperature-dependent enthalpies of mixing were calculated using the Monte Carlo method. Free energies of mixing were obtained by thermodynamic integration of the Monte Carlo results. The simulations suggest that the NaEuMo2O8 end-member is nearly fully ordered and has I[4 with combining macron] symmetry. The calculated subsolidus temperature-composition phase diagram is dominated by three miscibility gaps which are separated by narrow fields of stability of two ordered phases with the compositions of x = 4/9 and x = 2/3, where x is the mole fraction of the NaEuMo2O8 end-member.

Graphical abstract: Subsolidus phase relations in Ca2Mo2O8–NaEuMo2O8-powellite solid solution predicted from static lattice energy calculations and Monte Carlo simulations

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Publication details

The article was received on 01 Feb 2008, accepted on 28 Mar 2008 and first published on 01 May 2008


Article type: Paper
DOI: 10.1039/B801912F
Phys. Chem. Chem. Phys., 2008,10, 3509-3518

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    Subsolidus phase relations in Ca2Mo2O8–NaEuMo2O8-powellite solid solution predicted from static lattice energy calculations and Monte Carlo simulations

    V. L. Vinograd, D. Bosbach, B. Winkler and J. D. Gale, Phys. Chem. Chem. Phys., 2008, 10, 3509
    DOI: 10.1039/B801912F

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