Reversed Stability of Zirconium Oxide Dimer Isomers Triggered by Electron Gain or Removal

The neutral zirconium oxide dimer and its cationic and anionic counterparts were investigated using advanced ab initio electronic structure methods and flexible basis sets. The exploration of the ground-state potential energy surfaces of (ZrO₂)₂, (ZrO₂)₂⁺, and (ZrO₂)₂^- led to the identification of stable isomeric structures and their relative energies. It was found that (ZrO₂)₂ adopts three distinct isomeric forms resembling chair-, boat-, and scepter-like structures in its neutral, cationic, and anionic forms. The energetic ordering of these isomers in the neutral dimer is reversed upon either electron attachment or detachment. The adiabatic ionization potential of (ZrO₂)₂ was determined to be 9.141 eV, while the adiabatic electron affinity was found to be 1.475 eV. The vertical electron detachment energies were predicted to be 1.949, 1.852, and 1.340 eV, while the vertical ionization potentials, not previously reported in the literature, were determined to be 9.282, 9.375, and 9.594 eV. In both cases, the values correspond to the scepter, boat, and chair isomers, respectively, with the electron detachment energies showing excellent agreement with experimental data. Finally, possible scenarios of isomeric interconversion within the same charge, driven by electron attachment or detachment, were described and analyzed.