Optical response of metallic and insulatingVO2 calculated with the LDA approach

Abstract

We calculated the optical response of metallic and insulatingVO2 using the local density approximation (LDA) approach. The band structure calculation was basedon the full-potential linear-muffin-tin method. The imaginary part of the dielectric functionε2(ω) is related to the different optical transitions. The Drude tail in the calculation of themetallic phase corresponds to intraband d–d transitions. The calculation in theinsulating phase is characterized by the transitions to the band. The low-frequency features, 0.0–5.0 eV, correspond to V 3d–V 3d transitions, whereasthe high-frequency structures, 5.0–12 eV, are related to O 2p–V 3d transitions.The calculation helps to explain the imaginary part of the dielectric functionε2(ω), as well as the electron-energy-loss and reflectance spectra. The results reproduce not onlythe energy position and relative intensity of the features in the spectra, but also the mainchanges across the metal–insulator transition and the polarization dependence. The maindifference is a shift of about 0.6 eV in the calculation of the insulating phase. Thisdiscrepancy arises because the LDA calculation underestimates the value of the band gap.