Ab initio structures and stabilities of doubly charged diatomic metal helides for the first row transition metals

The electronic structure and molecular properties of doubly charged transition metal helides, HeX²⁺ (where X = Sc−Cu), have been investigated using the all-electron ROHF−UCCSD(T) method. Basis sets have been developed for the first row transition metals to elucidate trends in bonding, dissociation energies, and vibrational frequencies. The ground state for all the doubly charged helides exhibited a 3dⁿ configuration. In addition, states with configurations that have holes in the metal 3dσ orbital exhibited greater binding energies. Relativistic effects have also been investigated using the Cowan-Griffin ansatz. Anharmonic vibrational frequencies have been determined variationally