Nucleation of NaCl from aqueous solution: critical sizes, ion-attachment kinetics, and rates

Zimmermann, Nils E.R. and Vorselaars, Bart and Quigley, David and Peters, Baron (2015) Nucleation of NaCl from aqueous solution: critical sizes, ion-attachment kinetics, and rates. Journal of the American Chemical Society, 137 (41). pp. 13352-13361. ISSN 0002-7863

Full content URL: http://dx.doi.org/10.1021/jacs.5b08098

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Abstract

Nucleation and crystal growth are important in material synthesis, climate modeling, biomineralization, and pharmaceutical formulation. Despite tremendous efforts, the mechanisms and kinetics of nucleation remain elusive to both theory and experiment. Here we investigate sodium chloride (NaCl) nucleation from supersaturated brines using seeded atomistic simulations, polymorph-specific order parameters, and elements of classical nucleation theory. We find that NaCl nucleates via the common rock salt structure. Ion desolvation - not diffusion - is identified as the limiting resistance to attachment. Two different analyses give approximately consistent attachment kinetics: diffusion along the nucleus size coordinate and reaction-diffusion analysis of approach-to-coexistence simulation data from Aragones et al. [J. Chem. Phys., 2012, 136, 244508]. Our simulations were performed at realistic supersaturations to enable the first direct comparison to experimental nucleation rates for this system. The computed and measured rates converge to a common upper limit at extremely high supersaturation. However, our rate predictions are between 15 and 30 orders of magnitude too fast. We comment on possible origins of the large discrepancies.

Additional Information:150915125842009
Keywords:nucleation, NaCl, desolvation, diffusion, Molecular dynamics, JCOpen
Subjects:F Physical Sciences > F343 Computational Physics
F Physical Sciences > F310 Applied Physics
Divisions:College of Science > School of Mathematics and Physics
ID Code:18890
Deposited On:16 Oct 2015 09:24

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