Electronic Structure of Trioxide, Oxoperoxide, Oxosuperoxide, and Ozonide Clusters of the 3d Elements: Density Functional Theory Study

The trioxide clusters with stoichiometry MO₃, and the structural isomers with side-on and end-on bonded oxygen atoms, are studied by DFT with the B1LYP functional. For the first half of the 3d elements row (Sc to Cr), pyramidal or distorted pyramidal structures dominate among the trioxide and oxoperoxide ground states, while the remaining elements form planar trioxides, oxoperoxides, oxosuperoxides, and ozonides. Low-lying trioxide clusters are formed by Ti, V, Cr, and Mn, among which the distorted pyramidal VO₃ in the ²A′′ state, the pyramidal CrO₃ in the ¹A₁ state, and the planar MnO₃ in the ²A₁′ state are global minima. With the exception of the middle-row elements Mn, Fe, and Co, the magnetic moment of the ground-state clusters is formed with a major contribution from unpaired electrons located at the oxygen atoms. The stability of trioxides and oxoperoxides toward release of molecular oxygen is significantly higher for Sc, Ti, and V than for the remaining elements of the row. A trend of increasing the capability to dissociate one oxygen molecule is observed from Cr to Cu, with the exception of OFe(O₂) being more reactive than OCo(O₂). A gradual increase of reactivity from Ti to Cu is observed for the complete fragmentation reaction M + O + O₂.