Ground and Excited States of 3d and 4d Transition Metals: Computational Insight into Atomic Properties

Effective strategies for the computational prediction and ordering of the ground and low-lying excited states of 3d and 4d transition metal atoms can be difficult to achieve due to their high density of states, multiple spins, and narrow energy gaps. In this work, the energy manifolds for first- and second-row transition metal atoms were investigated using the super-correlation consistent Composite Approach (s-ccCA) and several multireference wave function approaches in combination with the correlation consistent basis sets. Scalar relativistic effects were also incorporated. The impact of these choices on the prediction of these energies was analyzed. Multireference configuration interaction with the Davidson correction (MRCI+Q) offers great reliability and accuracy for most transition metal atoms when extrapolated to the complete basis set limit. In a comparison of methodologies, s-ccCA results in the lowest deviation from experiment.