Study of the geometry of KCl clusters nucleating from vapour and in aqueous solutions

Abstract

The molecular interaction model of cluster formation was used to compute the formation energy of KCl clusters having ions from 4 to ca 10000, taking into consideration repulsion forces between ions. Four types of cluster geometries were analysed: spherical, cube-shaped (perfect cubes or cuboids with steps on one of their {1 0 0} faces) and octahedral with {1 1 1} and {1 1 1} 2 faces. It was found that cube-shaped clusters forming from the vapour phase are always preferential (more abundant) due to Coulomb interactions. In aqueous solutions, the subcritical clusters, both spherical and cube-shaped, can be preferential. Larger KCl clusters should have the cubic geometry due to the small values of the average adsorption energy of water molecules on their surface. Spherical and octahedral {1 1 1} 2 clusters adsorb water molecules more strongly, which leads to their significantly lower growth.