Systematic study of ore, peroxo, and superoxo isomers of 3d-metal dioxidesand their anions

The electronic and geometrical structures of the ground and excited states of the 3d-metal dioxides ScO2, TiO2, VO2, CrO2, MnO2, FeO2, CoO2, NiO2, CuO 2, and ZnO2 along with their singly charged negative ions have been calcula ted using the density functional theory with generalized gradient approxima tion for the exchange-correlation potential. We have considered ore, peroxo , and superoxo isomers in both neutral and anionic series. The ground state s of all 3d-metal dioxides and their anions possess oxo forms, except for c opper dioxide, which prefers a superoxo form. All the dioxides have a large number of isomers closely spaced in total energy. The champion, FeO2-, pos sesses five isomers within an energy range of 0.35 eV. The energy gap betwe en ore, peroxo, and superoxo isomers decreases along the series from TiO2 t o ZnO2. ScO2 has peroxo and superoxo isomers which are close in total energ y to its oxo ground state. The electron affinities are computed for all typ es of isomers and are compared to available experimental data. On the avera ge, our theoretical values are within 0.2 eV from the corresponding experim ental data. All the ground-state dioxides and their anions are found to be thermodynamically stable except for ZnO2, which is unstable toward dissocia tion of molecular oxygen.