SEARCH Articles Figures Tables Atomic orbitals core correlation Atomic orbitals core energy level Core carbon orbitals Core electrons molecular orbital theory Core orbital Core orbital Core orbital radius Effective core potentials coupled-cluster spin-orbit effects Frozen-core orbitals Frozen-core spin-orbit Hamiltonian Molecular orbital theory effective core potentials Orbitals core-penetrating Spin-orbit operators relativistic effective core potential Spin-orbit operators relativistic effective core potentials-based Valence orbitals, “core-like