Electric Potentials of Metastable Salt Clusters

EO Fetisov and WC Isley and GJ Lumetta and SM Kathmann, JOURNAL OF PHYSICAL CHEMISTRY C, 123, 14010-14023 (2019).

DOI: 10.1021/acs.jpcc.9b02494

Electric potentials and fields experienced by the ions in small metastable NaCl clusters and cubic crystals in vacuum and aqueous electrolyte solutions are used to characterize features underlying condensed-phase nucleation. The range of electrostatic potentials and fields experienced by NaCl nanocrystals and metastable clusters is analyzed using point charges and quantified as a function of particle size and charge state. We show how the potentials and fields of these crystals can be classified into various subgroups corresponding to corners, edges, faces, and interior sites. The differences between the interior and face potentials are correlated with the interfacial surface energy. This, in turn, influences cluster free energies and their corresponding populations in solution. As a result, the nucleation rate is correlated to these potentials through the formalism of classical nucleation theory. Additionally, we consider the importance of representation of the charge density, comparing point charge and continuous densities obtained from the quantum mechanical electronic structure. A key result of this work is the identification of the electric potential as a possible order parameter to understand nucleation pathways.

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