Charge-transfer energy in closed-shell ion–atom interactions

Abstract

The importance of charge‐transfer energy in the interactions between closed‐shell ions and atoms is investigated. Ab initio calculations on H⁺–He and Li⁺–He are used as a guide for the construction of approximate methods for the estimation of the charge‐transfer energy for more complicated systems. For many alkali ion–rare gas systems the charge‐transfer energy is comparable to the induction energy in the region of the potential minimum, although for doubly charged alkaline‐earth ions in rare gases the induction energy always dominates. Surprisingly, an empirical combination of repulsion energy plus asymptotic induction energy plus asymptotic dispersion energy seems to give a fair representation of the total interaction, especially if the repulsion energy is parameterized, despite the omission of any explicit charge‐transfer contribution. More refined interaction models should consider the charge‐transfer energy contribution.