ELECTRON-DENSITY OF THE TWIN-FREE ORTHORHOMBIC YBA2CU3O7-X SINGLE-CRYSTALS

The electron density maps of twin-free orthorhombic YBa2Cu3O7-x single crystal were calculated from the refinement of X-ray structure analys is. The YBa2Cu3O7-x single crystal was grown by the top-seeded crystal pulling method. Uniaxial pressure was applied in oxygen annealing pro cess to manufacture a twin-free orthorhombic single crystal. The cryst al structures of YBa2Cu3O7-x with a superconducting transition tempera ture of 91 K were determined by four-circle X-ray diffractometer. Crys tal data: M(r):666.4, orthorhombic, Pmmm, a = 3.8278 (7), b = 3.8952 ( 7), c = 11.711 (2) Angstrom, V = 174.61 (5) Angstrom(3), Z = 1, D-x = 6.317 Mgm(-3), lambda(Mo K-alpha) = 0.71069 Angstrom, mu(Mo K-alpha) = 282.77 cm(-1). The final values of the weighted reliability factor (R (w)) and unweighted factor (R) were 0.031 and 0.026 enable us to analy ze Fourier difference maps.