Electronic behavior of Ag-doped YBa2Cu3O7-δ using Hubbard-U correction method

Abstract

The ability to accurately describe the electronic properties in the highly correlated materials YBa2-xAgxCu3O7-δ was queried. Previous calculations revealed that the electronic bandgap was estimated much lower than the established experimental value when standard density functional theory, DFT was used in the computation of pure YBa2Cu3O7-δ. The electronic properties of Ag-doped at Ba-site samples such as the bandgap, total and partial density of states, electron density, and Mulliken population, were computationally calculated using DFT with the Hubbard-U correction method, DFT+U and compared to the pure samples. The calculation was conducted using CASTEP code in Material Studio software applying both LDA and range of GGA exchange-correlation functionals. 2 × 2 × 1 supercell symmetry was applied to enlarge the single cell crystal structure to able the dopant concentration, x = 0.250 at the Ba-site. The calculated bandgap of pure YBa2Cu3O7-δ (Eg = 3.67 eV) shows 8.25% difference to the referred theoretical value using the GGA-PBE+U functional. Upon Ag-dopant, the bandgap was calculated to be Eg = 3.85 eV. The energy of the Ba 6p orbital on the valence band has shifted from − 10.49 eV to − 10.67 eV, away from the Fermi energy level, and the density of state has increased significantly by + 57.52%. The Ag dopant enhanced the electron density of Cu and O atoms along the CuO chain and CuO2 plane. The study enables the prediction of impurity dopant concentration prior to experimental work, hence promoting green research.