A study on structural and electronic properties of Ag and Sb-doped in Ba-site of YBa2Cu3O7-δ superconductor via computational method / Siti Fatimah Saipuddin

The structural and electronic properties of YBa2Cu3O7-δ superconductors doped with Ag and Sb have been predicted theoretically. The Ag ionic radius of 126 pm matches the Ba atom, which is 134 pm, promoting electrical conductivity. When an Sb atom with a lower ionic radius of 76 pm is doped into the Ba-site of YBa2Cu3O7-δ, it undergoes structural modifications. To further understand its interatomic behaviour, the structural and electronic properties of both elements doped at the Ba-site of YBa2Cu3O7-δ were computationally analysed, over a wide range of dopant percentages. Focuses were made at x = ±0.200, where Ag dopant enhanced electrical conductivity, and Sb dopant provided structural alterations from prior experiments. The CASTEP computer code was applied employing various exchange-correlation functionals such as Local Density Approximation and Generalized Gradient Approximation on standard DFT (LDA CA-PZ, GGA-PBE, GGA-PBEsol, and GGA-WC) with the VCA technique and 2x2x1 supercell Hubbard U correction method, DFT+U (LDA CA-PZ+U, GGA-PBE+U, GGA-PBEsol+U, and GGA-WC+U) with U = 10.0 eV. Based on the computational calculation, the GGA-PBEsol and GGA-PBEsol+U give the best-validated results as compared to the referred experimental and theoretical studies. The lattice parameters of all samples differ by less than 5% from the previous experimental investigation.