Accurate reproduction of strongly repulsive interatomic potentials
Susi Lehtola
Abstract
Knowledge of the repulsive behavior of potential energy curves $V(R)$ at $R\ensuremath{\rightarrow}0$ is necessary for understanding and modeling irradiation processes of practical interest. $V(R)$ is in principle straightforward to obtain from electronic structure calculations; however, commonly used numerical approaches for electronic structure calculations break down in the strongly repulsive region due to the closeness of the nuclei. In this work, we show by comparison to fully numerical reference values that a recently developed procedure [S. Lehtola, J. Chem. Phys. 151, 241102 (2019)] can be employed to enable accurate linear combination of atomic orbitals calculations of $V(R)$ even at small $R$ by a study of the seven nuclear reactions ${\mathrm{He}}_{2}\ensuremath{\rightleftharpoons}\mathrm{Be}, \mathrm{HeNe}\ensuremath{\rightleftharpoons}\mathrm{Mg}, {\mathrm{Ne}}_{2}\ensuremath{\rightleftharpoons}\mathrm{Ca}, \mathrm{HeAr}\ensuremath{\rightleftharpoons}\mathrm{Ca}, \mathrm{MgAr}\ensuremath{\rightleftharpoons}\mathrm{Zn}, {\mathrm{Ar}}_{2}\ensuremath{\rightleftharpoons}\mathrm{Kr}$, and $\mathrm{NeCa}\ensuremath{\rightleftharpoons}\mathrm{Zn}$.