Evaluation of the B3LYP and HSE06 density functionals in the calculation of spectroscopic properties of the HCl2+ dication

Abstract

Potential energy curves (PECs) of the lowest singlet and triplet states of the HCl2+ dication have been calculated using density functional theory with the B3LYP and HSE06 functionals and coupled cluster CCSD(T) method, all with 6-311G(3df,3pd) basis set. Analysis of the results of all three methods shows that the triplet state is a pure 3Σ− state, while the singlet state is a mixture of the 1Δ and 1Σ+ states. Spectroscopic constants and Franck–Condon factors corresponding to the transitions from the ground state neutral HCl to these dicationic states have been calculated and compared to the available experimental and computational data. While the calculated spectroscopic constants and equilibrium bond lengths of the PECs obtained by the HSE06 functional are in good agreement with the available data, the predicted vertical offset of the PECs differ significantly with those observed experimentally. Inclusion of a set of floating basis functions corresponding to the Li ghost atom does not improve the results within the available experimental resolution. Addition of centrifugal term to the potential energy decreases the well depth and well width at barrier and increases the barrier height.