On the asymmetry in molybdenum-oxygen bonding in the MoO structure: ETS-NOCV analysis

In the present study, the analysis of natural orbitals for chemical valence (NOCV) combined with the extended-transition-state (ETS) bond-energy decomposition method (ETS-NOCV) was applied to characterize an asymmetry in Mo-O bonding in MoO crystal. Considered were three non-equivalent oxygen sites (O1, O2, O3) in the Mo O H cluster model of (010) surface of MoO . The ETS-NOCVmethod leads to the conclusion that an increase in the Mo-O distances, from 1.68 Å (for Mo-O1), through 1.73 Å (for Mo-O2), up to 1.94 Å (for Mo-O3), is directly related to decrease in strength of both σ-and π-contributions of Mo-O bond. Further, Mo-O connection appeared to exhibit both ionic (the charge transfer from 2p orbital of oxygen to molybdenum) and the covalent (charge accumulation in the region of Mo-O) components. Finally, the trend in the orbital energy stabilization (δEorb) originating from the dominant σ-and π-bond contributions appeared to correlate very well with the oxygen-vacancy formation energies published earlier by Tokarz-Sobieraj et al. (Surf Sci 489:107, 2001). © 2012 Springer Science+Business Media, LLC.