Theoretical studies of transition-metal hydrides. 2. CaH⁺ through ZnH⁺

We present consistent ab initio calculations (generalized valence bond plus configuration interaction) of the spectroscopic parameters for the ground and low-lying electronic states of the diatomic transition-metal hydrides CaH⁺ through ZnH⁺. We examine, in detail, the competing factors affecting metal hydride bonding: (1) the relative energies of the metal low-lying electronic states; (2) the intrinsic bond strength of H to various size 4s, 3d, or hybridized metal orbitals; and (3) the loss of high-spin metal exchange energy on bonding.