A novel analytical potential function for dicationic diatomic molecular systems based on deformed exponential function

Abstract

In this paper, we propose a new alternative analytical function aiming to better describe the potential energy curves of the doubly charged diatomic molecules. To achieve this goal, we modified an existing potential function in the literature to describe dicationic diatomic molecules using the deformed exponential function. We generated the potential energy curve of the testing group of dicationic diatomic molecules $\mathrm{B}{\mathrm{e}}_2^{2+}$, BH²⁺, $\mathrm{H}{\mathrm{e}}_2^{2+}$ and NH²⁺ by means of the CCSD(T)/aug-cc-pVQZ level of theory. To validate this new function, we also calculated the spectroscopic constants and the rovibrational spectra for the electronic state ${X}^1{\varSigma}_g^{+}$of the $\mathrm{B}{\mathrm{e}}_2^{2+}$ and $\mathrm{H}{\mathrm{e}}_2^{2+}$ systems using the Dunham and discrete variable representation methods. For BH²⁺ and NH²⁺ molecules, despite exhibiting a local minimum in the potential energy curve, no vibrational levels are supported, so the spectroscopic constants for these poorly bound systems are invalidated. The fitting accuracy had a better performance over the original potential for describing dicationic diatomic systems, considering that the discrete variable representation method resulted in a similar vibrational structure described in the literature. This fact can be explained due to the deformed function’s flexibility.