Evolution of the d∥ band across the metal-insulator transition in VO2

We studied the evolution of the electronic structure of VO2 across the metal-insulator transition. The electronic structure was calculated using the standard TB-LMTO-ASA method. The calculated DOS was compared to previous photoemission and X-ray absorption spectra. The electronic structure is discussed in terms of the usual molecular-orbital scheme. In the metallic phase, the d∥ band appears at the bottom of the V 3d bands and crosses the Fermi level. In the insulating phase, the d∥ band is split around 2 eV opening a pseudo band gap at the Fermi level. The largest effect of the splitting appears in the unoccupied part of the d∥ band. The calculated value of the splitting accounts for 77% of the experimental value, 2.6 eV. The results suggest that electron-lattice interaction seems to be the dominant factor in the splitting of the d∥ band.