Localized Electrons Around Cu Atoms of Superconductor, Tetragonal YBa2Cu3-xO7-y

Abstract
Crystal structure of tetragonal YBa2Cu2.93O6.38 has been determined by the single-crystal X-ray diffraction method. The space group is P4/mmm with lattice constants: a = 3.860(1) Å, c = 11.813(4) Å, and V = 176.05(7) Å3. The structure refinement has been successfully carried out with the final R value of 0.019(Rw=0.020). A difference-Fourier map reveals the existence of localized d-electrons around Cu2 atoms in the unit cell, although the electrons of Cul atoms have a spherical distribution.