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Structure, equation of state and transport properties of molten calcium carbonate (CaCO3) by atomistic simulations


Vuilleumier, Rodolphe; Seitsonen, Ari; Sator, Nicolas; Guillot, Bertrand (2014). Structure, equation of state and transport properties of molten calcium carbonate (CaCO3) by atomistic simulations. Geochimica et Cosmochimica Acta, 141:547-566.

Abstract

First-principle molecular dynamics (FPMD) calculations have been performed to evaluate the physical properties of liquid calcium carbonate (CaCO3), which are up to now poorly known. The liquid structure, the density, the atomic vibration motions, the diffusion coefficients of calcium and carbonate ions and the electrical conductivity have been evaluated. As compared with silicate melts, molten CaCO3 is characterized by a low density (∼2.25 g/cm3 at 1623 K and 0.5 GPa), a viscosity almost as low as that of water (∼5 mPa s), and a high conductivity (∼200 S/m). In using the FPMD calculations for benchmark, an empirical force field has been developed for predicting the properties of molten CaCO3 at any state point in the liquid stability field. This force field is implemented into a classical molecular dynamics (MD) code, much cheaper in computer time, and the equation of state and the phase diagram of the liquid phase have been obtained. The evolutions of the self diffusion coefficients, viscosity, and the electrical conductivity with pressure and temperature have been investigated and the results fitted with analytical forms. It is shown that the Stokes–Einstein equation, expressing the viscosity as a function of diffusion motion, is well followed, and that the Nernst–Einstein equation relating the electrical conductivity to the diffusion coefficients of charge carriers leads to an accurate prediction of the conductivity, provided that a constant correcting factor is applied. Consequently, viscosity and electrical conductivity of the liquid are found to be anticorrelated with each other and can be described by a simple law; λ = A/η0.9 (where A = 1.905, λ is in S/m, and η in Pa s).

Abstract

First-principle molecular dynamics (FPMD) calculations have been performed to evaluate the physical properties of liquid calcium carbonate (CaCO3), which are up to now poorly known. The liquid structure, the density, the atomic vibration motions, the diffusion coefficients of calcium and carbonate ions and the electrical conductivity have been evaluated. As compared with silicate melts, molten CaCO3 is characterized by a low density (∼2.25 g/cm3 at 1623 K and 0.5 GPa), a viscosity almost as low as that of water (∼5 mPa s), and a high conductivity (∼200 S/m). In using the FPMD calculations for benchmark, an empirical force field has been developed for predicting the properties of molten CaCO3 at any state point in the liquid stability field. This force field is implemented into a classical molecular dynamics (MD) code, much cheaper in computer time, and the equation of state and the phase diagram of the liquid phase have been obtained. The evolutions of the self diffusion coefficients, viscosity, and the electrical conductivity with pressure and temperature have been investigated and the results fitted with analytical forms. It is shown that the Stokes–Einstein equation, expressing the viscosity as a function of diffusion motion, is well followed, and that the Nernst–Einstein equation relating the electrical conductivity to the diffusion coefficients of charge carriers leads to an accurate prediction of the conductivity, provided that a constant correcting factor is applied. Consequently, viscosity and electrical conductivity of the liquid are found to be anticorrelated with each other and can be described by a simple law; λ = A/η0.9 (where A = 1.905, λ is in S/m, and η in Pa s).

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2014
Deposited On:03 Jan 2015 19:51
Last Modified:05 Apr 2016 18:42
Publisher:Elsevier
ISSN:0016-7037
Publisher DOI:https://doi.org/10.1016/j.gca.2014.06.037

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