“…Here we took into consideration the strong Coulomb interactions for the localized d electrons of Fe and Cr as well, therefore introducing the U term parameter for the 3d states of Cr and the 3d states of Fe. The choice for the Hubbard term in this work was 4 eV for Cr and 6.4 for Fe, in accordance with previous work 38 , 39 . Figure 4 DOS of Cr-doped TiO 2 with Cr as interstitial dopant (Cr i ) under biaxial tensile stress of ( a ) 0 GPa ( b ) 4 GPa ( c ) 8 GPa and DOS of TiO 2 with Cr as substitutional dopant (Cr Ti ) under biaxial tensile stress of ( d ) 0 GPa ( e ) 4 GPa and ( f ) 8 GPa .…”
Section: Resultssupporting
confidence: 57%
“…In our calculations the generalized-gradient approximation along with the Hubbard U correction was applied. The parameter U set to 8.2 eV for the Ti 3d orbitals, 4 eV for Cr 3d orbitals and 6.4 eV for Fe 3d orbitals 14 , 38 , 39 .…”
Anatase titanium oxide is important for its high chemical stability and photocatalytic properties, however, the latter are plagued by its large band gap that limits its activity to only a small percentage of the solar spectrum. In that respect, straining the material can reduce its band gap increasing the photocatalytic activity of titanium oxide. We apply density functional theory with the introduction of the Hubbard + U model, to investigate the impact of stress on the electronic structure of anatase in conjunction with defect engineering by intrinsic defects (oxygen/titanium vacancies and interstitials), metallic dopants (iron, chromium) and non-metallic dopants (carbon, nitrogen). Here we show that both biaxial and uniaxial strain can reduce the band gap of undoped anatase with the use of biaxial strain being marginally more beneficial reducing the band gap up to 2.96 eV at a tensile stress of 8 GPa. Biaxial tensile stress in parallel with doping results in reduction of the band gap but also in the introduction of states deep inside the band gap mainly for interstitially doped anatase. Dopants in substitutional positions show reduced deep level traps. Chromium-doped anatase at a tensile stress of 8 GPa shows the most significant reduction of the band gap as the band gap reaches 2.4 eV.
“…Here we took into consideration the strong Coulomb interactions for the localized d electrons of Fe and Cr as well, therefore introducing the U term parameter for the 3d states of Cr and the 3d states of Fe. The choice for the Hubbard term in this work was 4 eV for Cr and 6.4 for Fe, in accordance with previous work 38 , 39 . Figure 4 DOS of Cr-doped TiO 2 with Cr as interstitial dopant (Cr i ) under biaxial tensile stress of ( a ) 0 GPa ( b ) 4 GPa ( c ) 8 GPa and DOS of TiO 2 with Cr as substitutional dopant (Cr Ti ) under biaxial tensile stress of ( d ) 0 GPa ( e ) 4 GPa and ( f ) 8 GPa .…”
Section: Resultssupporting
confidence: 57%
“…In our calculations the generalized-gradient approximation along with the Hubbard U correction was applied. The parameter U set to 8.2 eV for the Ti 3d orbitals, 4 eV for Cr 3d orbitals and 6.4 eV for Fe 3d orbitals 14 , 38 , 39 .…”
Anatase titanium oxide is important for its high chemical stability and photocatalytic properties, however, the latter are plagued by its large band gap that limits its activity to only a small percentage of the solar spectrum. In that respect, straining the material can reduce its band gap increasing the photocatalytic activity of titanium oxide. We apply density functional theory with the introduction of the Hubbard + U model, to investigate the impact of stress on the electronic structure of anatase in conjunction with defect engineering by intrinsic defects (oxygen/titanium vacancies and interstitials), metallic dopants (iron, chromium) and non-metallic dopants (carbon, nitrogen). Here we show that both biaxial and uniaxial strain can reduce the band gap of undoped anatase with the use of biaxial strain being marginally more beneficial reducing the band gap up to 2.96 eV at a tensile stress of 8 GPa. Biaxial tensile stress in parallel with doping results in reduction of the band gap but also in the introduction of states deep inside the band gap mainly for interstitially doped anatase. Dopants in substitutional positions show reduced deep level traps. Chromium-doped anatase at a tensile stress of 8 GPa shows the most significant reduction of the band gap as the band gap reaches 2.4 eV.
“…U ¼ 4:0 eV was obtained as a proper value for Sn 4d electrons after parameterization was performed previously. 32 Introduction of Hubbard U-like term allows getting a band gap width equal to 1.93 eV. That is considerably larger as band gap value of 1.14 eV obtained by the standard DFT approach and thus justi¯es the use of the GGA þ U.…”
First-principles calculations based on the density functional theory (DFT) within the generalized gradient approximation have been used in the present research. Fluorine doping in the SnO 2 crystals has been carried out considering a number of different defect concentrations. Dopant influence upon structural, electronic and electrical properties of the tin dioxide has been discussed in detail. The system presents n-type electrical conductivity relating our work directly to a number of empirical studies in this area. An experimental fact that n-type conductivity tends to decrease at rather high fluorine impurity rates has been explained at the theoretical level.
“…The changes of bandgap and energy band cannot affect the electronic structure analysis of SnO 2 crystals. The bandgap value can be modified by the complex variable function method (DFT + U) [20] to obtain a more accurate bandgap value. Although there are still some issues needed to be solved with this method, it is sufficient to mainly discuss the photoelectric properties of doped SnO 2 .…”
Section: Band Structure and Density Of Statesmentioning
Crystal structure and electronic properties of SnO2 doped with non-metal elements (F, S, C, B, and N) were studied using first-principles calculations. The theoretical results show that doping of non-metal elements cannot change the structure of SnO2 but result in a slight expansion of the lattice volume. The most obvious finding from the analysis is that F-doped SnO2 has the lowest defect binding energy. The doping with B and S introduced additional defect energy levels within the forbidden bandgap, which improved the crystal conductivity. The Fermi level shifts up due to the doping with B, F, and S, while the Fermi level of SnO2 doped with C or N has crossed the impurity level. The Fermi level of F-doped SnO2 is inside the conduction band, and the doped crystal possesses metallicity. The optical properties of SnO2 crystals doped with non-metal elements were analyzed and calculated. The SnO2 crystal doped with F had the highest reflectivity in the infrared region, and the reflectance of the crystals doped with N, C, S, and B decreased sequentially. Based on this theoretical calculations, F-doped SnO2 is found to be the best photoelectric material for preparing low-emissivity coatings.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
