Density Functional Characterization of the Electronic Structure and Visible‐Light Absorption of Cr‐Doped Anatase TiO₂

Abstract

To evaluate the electronic and optical properties of Cr-doped anatase TiO(2), three possible Cr-doped TiO(2) models, including Cr at a Ti site (model I), Cr at a Ti site with an oxygen vacancy compensation (model II), and an interstitial Cr site (model III), are studied by means of first principles density functional theory calculations. In model I, the splitting behavior of the Cr 3d states and the insulating properties are successfully depicted by the GGA+U method, from which it is proposed that Cr at a Ti site should exist as Cr(4+) instead of the generally believed Cr(3+). As a result, the electron transitions between these impurity states, the conduction band (CB), and the valence band (VB), as well as the d-d transitions between occupied and unoccupied Cr 3d states, provide a reasonable explanation for the experimentally observed major and minor absorption bands. In models II and III, the impurity states and associated optical transition processes-as well as the corresponding electron configurations-are examined.

Endowing single-electron-trapped oxygen vacancy self-modified titanium dioxide with visible-light photocatalytic activity by grafting Fe(III) nanocluster

“…The GGA + U method was used to calculate the DOS of TiO 2 and V 0 • -TiO 2 . The U parameter (Ueff = 5.8 eV [48] for the Ti 3d orbit) was used to reach an agreement with the experimental band gap of anatase TiO 2 . Anatase TiO 2 was modeled with a 2 × 2 × 2 super cell containing 32 Ti atoms and 64 O atoms.…”

Enhanced photocatalytic oxidation of propylene over V-doped TiO2 photocatalyst: Reaction mechanism between V5+ and single-electron-trapped oxygen vacancy

“…The electronic structures of the corresponding optimized geometries was calculated by GGA + U method. To reach an agreement with the experimental band gap of anatase TiO 2 , the U parameter (U eff = 5.8 eV [50] for the Ti 3d orbit and U eff = 7.0 eV [51] for the V 3d orbit) was used. A 2 × 2 × 2 supercell containing 32 Ti atoms and 64 O atoms was simulated for anatase TiO 2 .…”

Nitrogen vacancy and ferromagnetism in Cr-doped GaN: First-principles calculations

“…Therefore, the GGA and GGA+ U methods are both used in the calculation of the CrGa 35 N 36 configuration to test the performance of the on-site correlation by a Hubbard effective U term. Consider that the U parameter is applied to localized orbitals of specific atoms (normally the d or f levels of TM or rare-earth ions), we choose an effective interaction parameter U eff ¼3.0 for Cr 3d electrons in our calculations that is based on an earlier paper [34]. The GGA approach is implemented in DMol 3 and the GGA+ U approach is implemented in the CASTEP, so we first compare the results of the electronic band structures by using the GGA method in DMol 3 and Cambridge sequential total energy package (CASTEP) [35], respectively.…”