Structural analysis of Y3Ba5Cu8O19−δ high-Tc superconductor by ab initio density functional theory

Abstract

The details of the crystal structure of the recently discovered Y3Ba5Cu8O18+δ (Y358) superconductor have been determined by ab initio density functional theory. Total energy calculation has been performed for three different suggested structures with different oxygen content. The structure with a center of inversion symmetry and the highest oxygen concentration has the lowest total energy. Thus, it is the best choice for the Y358 crystal structure. By investigating the detailed structure, it is seen that this compound is arranged either of YBa2Cu3O7 and YBaCu2O5 or YBaCu2O5 and BaCuO2 substructural blocks in the c direction. The difference between the total energy of Y358 compound and the sum of its substructure blocks was found to be 0.00325Ry. The phase separation could occur by absorbing this energy for example during the sample preparation procedure.