Two-Component Relativistic Equation-of-Motion Coupled-Cluster Methods for Excitation Energies and Ionization Potentials of Atoms and Molecules.

Two-component relativistic equation-of-motion coupled-cluster methods are developed and implemented. Scalar-relativistic and spin-orbit effects are taken into account through a two-component scheme in both Hartree-Fock and correlation calculations. Excitation energies and spin-orbit splittings of atoms and diatomic molecules, and ionization potentials of OsO are reported. The advantage of the present two-component scheme is illustrated particularly for heavy-element systems.