Comparative study of the effect of the Hubbard coefficient U on the properties of TiO2 and ZnO

Comparative study of the effect of the Hubbard coefficient U on the properties of TiO2 and ZnO

[Display omitted] •In TiO2, as the U factor increases, both the BG and the unit cell parameters increase.•For ZnO, as U increases, BG increases but the structure parameters decrease.•The BG value reaches a maximum from which it decreases in the case of titania.•An increasing and linear behavior is o...

Full description

Saved in:
Bibliographic Details
Published in:Materials today communications Vol. 27; p. 102368
Main Authors: Fernández, A.C. Rossi, Schvval, A.B., Jiménez, M.J., Cabeza, G.F., Morgade, C.I.N.
Format: Journal Article
Language:English
Published: Elsevier Ltd 01-06-2021
Subjects:
DFT
Hubbard’s coefficient
TiO2 anatase
TiO2 rutile
Wurtzite ZnO
TiO2 anatase
Wurtzite ZnO
DFT
TiO2 rutile
Hubbard’s coefficient
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:[Display omitted] •In TiO2, as the U factor increases, both the BG and the unit cell parameters increase.•For ZnO, as U increases, BG increases but the structure parameters decrease.•The BG value reaches a maximum from which it decreases in the case of titania.•An increasing and linear behavior is observed for the BG width on ZnO.•The effects of Ud parameter are especially visible in CB for TiO2 and in VB for ZnO. First-principles calculations combined with Hubbard U correction based on Density Functional Theory has been used to investigate the effect of its inclusion on electronic, structural, and optical properties and to reproduce correct band gap for TiO2 (anatase and rutile) and ZnO (wurtzite) structures. The effect of the implementation of U for only metal (Ti or Zn) d state (Ud) or for both 3d (Ud) and Op (Up) states was investigated to exploring changes in valence and conduction bands and their origin. Bader’s charge analysis has been used to revealing the nature of chemical bonding. We can conclude that for both TiO2 polymorphs as the Ud factor increases, both the BG and the lattice parameter increase. On the contrary, for ZnO, as Ud increases the value of BG increases but the cell parameter decreases. The optimal values correspond to Ud =8 eV (TiO2) and Ud =13 eV (ZnO). The corresponding optical properties using Ud, such as real and imaginary parts of dielectric function, reflectivity R(ω), refractive index n(ω), extinction coefficient k(ω), absorption coefficient α(ω) and electron energy loss function L(ω) has been calculated. It is important to highlight that the curves obtained considering the inclusion of the Ud show an excellent agreement with those reported experimentally.
ISSN:2352-4928
2352-4928
DOI:10.1016/j.mtcomm.2021.102368