Relativistic equation-of-motion coupled-cluster method for the ionization problem: Application to molecules

TL;DR

This paper introduces a relativistic equation-of-motion coupled-cluster method for calculating molecular ionization potentials, demonstrating high accuracy and agreement with experimental data for various molecules.

Contribution

The paper presents the first implementation of a 4-component relativistic EOM-CCSD method for molecular ionization, including comparison with perturbation theory and experimental results.

Findings

Achieved less than 1% deviation from experimental ionization potentials.

Demonstrated the importance of electron correlation in ionization calculations.

Validated the method across multiple molecules with different halogens.

Abstract

We report the implementation of 4-component spinor relativistic equation-of-motion coupledcluster method within the single- and double- excitation approximation to calculate ionization potential (EOM-CCSD) of molecules. We have applied this method to calculate vertical ionization potentials of the molecules, XH(X=F, Cl, Br, I) along with Cl2 and Br2 in their closed-shell configuration. We have also presented intermediate results using 2-nd order many-body perturbation theory level in the EOM framework (EOM-MBPT(2)) to understand the role of electron correlation. All the calculated values are compared with the available experimental results. Our results are found to be in well agreement with the sophisticated experiments and relative deviation of less than 1% achieved for all the considered systems.