Publication: A simulation study of homogeneous ice nucleation in supercooled salty water
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2018-06-14
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Amer Inst Physics
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Abstract
We use computer simulations to investigate the effect of salt on homogeneous ice nucleation. The melting point of the employed solution model was obtained both by direct coexistence simulations and by thermodynamic integration from previous calculations of the water chemical potential. Using a seeding approach, in which we simulate ice seeds embedded in a supercooled aqueous solution, we compute the nucleation rate as a function of temperature for a 1.85 NaCl mol per water kilogram solution at 1 bar. To improve the accuracy and reliability of our calculations, we combine seeding with the direct computation of the ice-solution interfacial free energy at coexistence using the Mold Integration method. We compare the results with previous simulation work on pure water to understand the effect caused by the solute. The model captures the experimental trend that the nucleation rate at a given supercooling decreases when adding salt. Despite the fact that the thermodynamic driving force for ice nucleation is higher for salty water for a given supercooling, the nucleation rate slows down with salt due to a significant increase of the ice-fluid interfacial free energy. The salty water model predicts an ice nucleation rate that is in good agreement with experimental measurements, bringing confidence in the predictive ability of the model. We expect that the combination of state-of-the-art simulation methods here employed to study ice nucleation from solution will be of much use in forthcoming numerical investigations of crystallization in mixtures. Published by AIP Publishing.
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© 2018 Author(s). This work was funded by Grant Nos. FIS2013/43209-P and FIS2016-78117-P FIS2016-78847-P of the MEC and the UCM/Santander 910570 and PR26/16-10B-2. C. Valeriani and E. Sanz acknowledge financial support from a Ramón y Cajal Fellowship. J. R. Espinosa acknowledges financial support from the FPI Grant No. BES-2014-067625. Calculations were carried out in the supercomputer facilities La Palma and Magerit from the Spanish Supercomputing Network (RES) (Project Nos. QCM-2015-3-0036 and QCM-2016-1-0039). The authors acknowledge the computer resources and technical assistance provided by the Centro de Supercomputación y Visualización de Madrid (CeSViMa) and discussions with F. Caupin.