Nonadditivity of Temperature Dependent Interactions in Inorganic Ionic Clusters

Abstract

Nonadditivity of interactions implies, in the chemical context, that binding of atoms cannot be fully predicted from interactions between atom pairs. This phenomenon determines the identity of our world, which would have been much poorer otherwise. Ionic systems provide a good example of the interaction nonadditivity, which arises in most cases due to electron transfer and delocalization effects. Using Born-Oppenheimer molecular dynamics simulations of LiCl, NaCl, and KCl at 300, 1500, and 2000 K, we show that interaction nonadditivity originates from interplay of thermal motion and cation nature. in the case of alkali cations, ionic nature plays a more significant role than thermal effects. the nonadditivity is significant in all systems and at all temperatures considered. Dipole moments increase at higher temperatures due to thermal fluctuations and thermal expansion of the clusters. At the same time, ionic charges change little. Our results contribute to the fundamental understanding of electronic effects in nanoscale and condensed phase ionic systems, and foster progress in physical chemistry and engineering.