The Study of \({\text{Br}}_{{\text{2}}}^{ + }\) with Equation-of-Motion Coupled-Cluster Methods Including Spin-Orbit Coupling

The equation-of-motion coupled-cluster (EOM-CC) methods with spin-orbit coupling are used to study the low-lying states of \({\text{Br}}_{{\text{2}}}^{ + }\) . Spectroscopic constants and potential energy curves are mainly calculated using the EOM-CC and the approximate methods named EOM-CC (a) and EOM-CC (b). These two methods which are extended based on EOM-CC by us can reduce the computational effort for ionization potentials (IPs) and electron affinities (EAs) from N⁶ to N⁵. N is the system size. The results show that the EOM-CC method can accurately simulate the spectroscopic constants and potential energy curves of the low-lying states of \({\text{Br}}_{{\text{2}}}^{ + }\) . The EOM-CC (b) approximate method emerges as a favorable and highly agreeable alternative to the EOM-CC approach.