PNNL

Abstract

Small metastable NaCl clusters and cubic nanocrystals in vacuum and condensed aqueous electrolytes are used to characterize the electric potentials and fields experienced by the ions. The range of electrostatic potentials and fields experienced by NaCl nanocrystals and metastable clusters are analyzed using point charges, and quantified as a function of particle size and charge state. We show how the potentials and fields of these nanocrystals can be classified into various subgroups corresponding to corners, edges, faces, and interior sites. The difference between the interior and face potentials are correlated with the interfacial surface energy. This, in turn, influences cluster free energies and their corresponding populations. As a result, these potentials are correlated to the nucleation rate through the formalism of classical nucleation theory. Through this process, we consider the representation of the charge density, comparing point charge and continuous densities obtained from quantum mechanical electronic structure. A key result of this work is the identification of the electrical potential as an order parameter to understand nucleation pathways of salts. To do this, connection to the bulk Madelung potential reference must be established.