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Simulations of NaCl Aggregation from Solution: Solvent Determines Topography of Free Energy Landscape
Author(s) -
Patel Lara A.,
Kindt James T.
Publication year - 2019
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.25554
Subject(s) - supersaturation , chemistry , nucleation , cluster (spacecraft) , solvent , amorphous solid , partition (number theory) , molecular dynamics , chemical physics , thermodynamics , energy landscape , crystallography , computational chemistry , physics , organic chemistry , biochemistry , mathematics , combinatorics , computer science , programming language
The partition‐enabled analysis of cluster histograms (PEACH) method is used to calculate the free energy surface of NaCl aggregation using cluster statistics from MD simulations of small systems (40–90 ions plus solvent) in four solvents. In all cases (pure methanol, pure water, and two methanol/water mixtures) NaCl clusters show a transition from amorphous to rocksalt structure with increasing cluster size. The crossover sizes, and the apparent kinetic barrier to ordering, increase with increasing water content. Implications for the proposed two‐step mechanism of NaCl crystal nucleation (in which the ordered structure emerges from a large disordered cluster), and how this mechanism might depend on solvent and on degree of supersaturation, are discussed. In pure water, nonideal crowding effects that promote clustering are identified from systematic concentration‐dependent deviations between simulation results and the PEACH model fit. In contrast, the ability of PEACH to fit aggregation statistics in mixed solvents is consistent with negligible interactions between ions in different clusters. © 2018 Wiley Periodicals, Inc.