Nucleation of NaCl from Aqueous Solution: Critical Sizes, Ion-Attachment Kinetics, and Rates

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• 作者：Nils E. R. Zimmermann ; Bart Vorselaars ; David Quigley ; Baron Peters
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：October 21, 2015
• 年：2015
• 卷：137
• 期：41
• 页码：13352-13361
• 全文大小：615K
• ISSN：1520-5126

文摘

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鈥攏ot diffusion鈥攊s 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 discrepancy.