Coupled-cluster method for the electronic structure and spectroscopic constants in halohydride cations with spin?orbit coupling

Spin-orbit coupling (SOC) effects in equilibrium geometries, electron affinities and adiabatic excitation energies of the low-lying states for a series of halohydride cations are reported with the equation-of-motion coupledcluster method (EOM-SOC-CC) using relativistic effective core potentials. An approximation of this method, called EOM-SOC-CC-a, is introduced in order to reduce the computational effort for ionization potentials (IPs) without sacrificing accuracy significantly. SOC is increasingly important for the heavier halohydride cations and their calculated properties are well described by the EOM-SOC-CC method. As a cheap method, EOM-SOC-CC-a is recommended with satisfactory accuracy for the calculation of IPs up to the fifth row and the electronic structure up to the fourth row.

Automated summary

The effects of spin-orbit coupling in halohydride cations were investigated using the EOM-SOC-CC method, with SOC being increasingly important for heavier cations. An approximation method, EOM-SOC-CC-a, was introduced to reduce computational effort for ionization potentials while maintaining accuracy. Both methods provide satisfactory results for the electronic structure and IPs calculations.