  The article deals with the extension of the relativistic double-ionization
equation-of-motion coupled-cluster (DI-EOMCC) method [H. Pathak et al. Phys.
Rev. A 90, 010501(R) (2014)] for the molecular systems. The Dirac-Coulomb (DC)
Hamiltonian with four-component spinors is considered to take care of the
relativistic effects. The implemented method is employed to compute a few
low-lying doubly ionized states of noble gas atoms (Ar, Kr, Xe, and Rn) and Cl
2 , Br 2 , HBr, and HI. Additionally, we presented results with two
intermediate schemes in the four-component relativistic DI-EOMCC framework to
understand the role of electron correlation. The computed double ionization
spectra for the atomic systems are compared with the values from the
non-relativistic DI-EOMCC method with spin-orbit coupling (SOC) [Z. Wang et al.
J. Chem. Phys. 142, 144109 (2015)] and the values from the National Institute
of Science and Technology (NIST) database. Our atomic results are found to be
in good agreement with the NIST values. Further, the obtained results for the
molecular systems agree well with the available experimental values.

Chemical Physics