DFT + U method in determining Cu[sbnd]O bond length on CuO chain and CuO2 plane for pure, Ag, and Sb-doped YBa2-xRxCu3O7-δ

Abstract

Structural analysis of pure and doped superconductors based on computational calculations can be obtained by determining the bond lengths between cuprate layers as dopant is added to the molecular structure. When different charge and ionic radius impurity elements (Ag and Sb) were introduced into pure YBa2x RxCu3O7-δ superconductor, distortion was observed in comparison to the pure structure. The First Principle Study via Density Functional Theory with Hubbard U correction method (DFT + U) is used in this study to determine the structural behaviour of pure, Ag, and Sb-doped on 2 × 2 × 1 supercell YBa2x RxCu3O7-δ between the length of the Cu–O bond on CuO chain and CuO2 plane. The LDA CA-PZ(+U), GGA-PBE(+U), GGA-PBEsol(+U), and GGA-WC(+U) exchange–correlation functionals with U = 10.0 eV were given on the Cu 3d orbital. As Ag and Sb-dopant added separately on the CuO chain, the Cu(1)-O(1) bond length varied by 1.820Å≤lAg[Cu1-O1]≤1.945Å and 1.820Å≤lSb[Cu1-O1]≤2.056Å and the Cu(1)-O(4) bond length varied by 1.745Å≤lAg[Cu1-O4]≤1.880Å and 1.745Å≤lSb[Cu1-O4]≤1.977Å. The length of the Cu(2)-O(2) on CuO2 plane varied by 1.876Å≤lAg[Cu2-O2]≤2.003Å and 1.808Å≤lSb[Cu2-O2]≤1.973Å, the Cu(2)-O(3) changes by 1.883Å≤lAg[Cu2-O3]≤2.010Å and 1.941Å≤lSb[Cu2-O3]≤2.063Å while for Cu(2)-O(4), changes were observed between 1.816Å≤lAg[Cu2-O4]≤2.291Å and 1.816Å≤lSb[Cu2-O4]≤2.305Å. As the Ag atoms were added, the bond length along the x-y plane increased, indicating a repulsive force between the Ag atoms and the cuprates. The y-z plane decreased towards the Sb atoms when Sb dopant was substituted, demonstrating the attractive force between Sb and the Cu–O atoms. In the future, supporting electronic calculations may improve the findings obtained through structural analysis.