The structure of the bulk and the (001) surface of V2O5. A DFT+U study

Abstract

GGA(PW91)+Uis applied to the calculation of the structure (lattice parameters) and the electronic structure of theV2O5 bulk and its (001) surface for different values ofUeff used in the literature (0.0, 3.0 and 6.6 eV). Similar surface lattice parameters are calculated for the (001) surface and for the bulk, as well as similar electronic structures. The calculated lattice parameters (a and b for the surface and a, b and c for the bulk) are in good agreement with experimental results. It seems that there is no strong correlation between the calculated lattice parameters and the value ofUeff. The calculated width of the valence band keeps the value of 5 eVfor the three studiedUeff. However, the energy gap between the valence and the conduction bands increases with the value ofUeff.Ueff=3.0 eV seems to be the most adequate value to describe the energy gap after comparison with experimental results. Electronic density contour plots indicate that for a larger (smaller)Ueff the accumulated charge in the V-O(1) bond is overestimated (underestimated). The contour plots (in the a direction) show that the charge distribution V-O(3) is less correlated withUeff than the charge distribution V-O(1), whereas charge distribution V-O(2) seems not to be corretaled withUeff. The energy gap between the valence and the conduction bands seems to be strongly related with the charge distribution in the V-O(1) bond. The V-O(1) bond stability seems to be correlated withUeff. However, the stability of the V-O(2) and V-O (3) bonds seems not to be strongly affected byUeff.