Deposition of (WO{sub 3}){sub 3} nanoclusters on the MgO(001) surface: A possible way to identify the charge states of the defect centers

Periodic density functional theory calculations have been performed to study the most stable structure of the (WO{sub 3}){sub 3} nanocluster deposited on the MgO(001) surface with three kinds of F{sub S} centers (F{sub S}{sup 0}, F{sub S}{sup +}, and F{sub S}{sup 2+}). Our results indicate that the configuration of (WO{sub 3}){sub 3} cluster, including the cyclic conformation and the heights of three W atoms, and the oxidation states are sensitive to the charge state of the F{sub S} center. It is interesting that the electron-riched F{sub S}{sup 0} vacancy on the MgO(001) surface can act as a promoting site to enhance the W-W interaction and the W{sub 3}O{sub 3} cyclic conformation is maintained, while the skeleton of cluster becomes flexible when (WO{sub 3}){sub 3} is adsorbed on the electron-deficient vacancy (F{sub S}{sup +} and F{sub S}{sup 2+}). Accordingly, three F{sub S}-centers exhibit different arrangements of X-ray photoelectron spectra, the scanning tunneling microscopy images, and the vibrational spectra after depositing (WO{sub 3}){sub 3} cluster. Present results reveal that the (WO{sub 3}){sub 3} cluster may be used as a probe to identify the different F{sub S} centers on the MgO(001) surface.