Models of finely dispersed MgO and V2O5 on silica. Theoretical analysis of optical properties using TDDFT

Abstract

The results of Density Functional Theory (DFT) calculations on optical properties of vanadium complexes VOCl3, VOCl4-, VOCl52-, as well as the VO43- ion, are presented. The spectra of excited states in the range 25000-60000 cm-1 have been analyzed using the time-dependent DFT method (TDDFT). Spectroscopic features of structural defects (low-coordinated (LC) oxygen ions), as well as surface point defects (F+ and F sites) in MgO, have been studied within the cluster approach. The charge-transfer spectra and frequencies of normal vibrations for a number of active site models of finely dispersed oxides MgO and V2O5 on silica have been calculated. Comparison of the obtained results with experimental electronic diffuse reflectance spectra and fundamental frequencies confirms a hypothesis about the structure of active centers of finely dispersed oxide V2O5 on silica as monomeric forms, (O=V-On).