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

FERNÁNDEZ, A.C. ROSSI; SCHVVAL, A.B.; JIMÉNEZ, M.J.; CABEZA, G.F.; MORGADE, C.I.N.

Materials Today Communications

Elsevier

Año: 2021 vol. 27 p. 102368 - 102380

2352-4928

First-principles calculations combined withHubbard U correction based on Density Functional Theory has been used toinvestigate the effect of its inclusion on electronic, structural, and opticalproperties and to reproduce correct band gap for TiO2 (anatase andrutile) and ZnO (wurtzite) structures. The effect of the implementation of U foronly 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 bandsand their origin. Bader´s charge analysis has been used to revealing the natureof chemical bonding. We can conclude that for both TiO2 polymorphsas the Ud factor increases, both theBG and the lattice parameter increase. On the contrary, for ZnO, as Ud increases the value of BG increasesbut the cell parameter decreases. The optimal values correspond to Ud = 8 eV (TiO2) and Ud = 13 eV (ZnO). The correspondingoptical properties using Ud, such asreal and imaginary parts of dielectric function, reflectivity R(ω), refractiveindex n(ω), extinction coefficient k(ω), absorption coefficient α(ω) andelectron energy loss function L(ω) has been calculated. It is important tohighlight that the curves obtained considering the inclusion of the Ud show an excellent agreement with thosereported experimentally