Effect of Sb-doped YBa2-xSbxCu3O7-δ superconductor on electronic behaviour using density functional theory

Abstract

The modification upon Sb doping on Ba-site of YBa2-xSbxCu3O7-δ superconductor on its electronic behaviour has been studied by applying the Density Functional Theory (DFT) via first principle study. The properties were investigated via computational simulation adopting CASTEP computational code. The crystal structure was constructed and calculated using Visual Crystal Approximation (VCA) with Generalized Gradient Approximation Perdew Burke Ernzerhof (GGA PBE) exchange–correlation and ultrasoft pseudopotential. Geometry optimization at 4×4×1 k-point sampling shown energy converged at 400 eV. Computer simulation was used to determine the electronic modifications occurred between the CuO chain and CuO2 plane with Ba-site of Sb dopant. Generally, the YBa2-xSbxCu3O7-δ has orthorhombic crystal structure since the lattice parameters of a, b, and c are not the same. From the band structure analysis, the smallest bandgap was observed at x = 0.225 between its upper conduction (CV) and the lower valence band (VB). The electrons were found to be more concentrated towards the Fermi level when observed via its density of state distribution. In the electron density differences images, we can observe the merge of orbital configuration contributed by each atom upon doping at x = 0.225. From there we can say that on that Sb concentration, the YBa2-xSbxCu3O7- is optimum.