Thermodynamic Stability in Transition Metal-Hydrogen Dications: Potential Energy Curves, Spectroscopic Parameters, and Bonding for VH2+

Seventeen electronic states of the dication VH²⁺ were characterized by the SA-CASSCF/icMRCI methodology using very extended basis sets; 11 were described for the first time. Potential energy curves were constructed and the associated spectroscopic parameters evaluated. Triplet and quintet states correlating with the V²⁺ + H channel are thermodynamic stable. For states dissociating into the channel V⁺ + H⁺, avoided crossings at large distances give rise to thermodynamic metastability but do not affect the characterization of the bound region. Configuration state functions with the 3σ orbital /doubly occupied give rise to covalent contributions to the bonding; the major contribution, however, comes from the electrostatic charge-induced dipole interaction. This explains the shape and proximity of the potential energy curves beyond their equilibrium distances. Dipole moment functions and vibrationally averaged dipole moments quantify the polarity of the molecule. Spin–orbit couplings give rise to complex and dense regions of very close-lying Ω states.