ATOMIC-STRUCTURE OF HIGH-TEMPERATURE SUPERCONDUCTING (ND,CE)(2)CUO4-DELTA SINGLE-CRYSTALS

The atomic structure of high-temperature (T-c = 10 K) superconducting Nd1.85Ce0.15CuO4 - delta single crystals has been refined from X-ray d iffraction data (AgKalpha-radiation, 9040 measured reflections, 565 cr ystallographically nonequivalent reflections): sp, gr. I/4mmm, a = 3.9 486(5) Angstrom, c = 12.0846(11) Angstrom, R-w = 1.90%, R = 1.17%. The difference electron-density distribution was calculated and analyzed. The electron-density maps of doped crystals showed a redistribution o f the electron density in the vicinity of the Nd/Ce position in compar ison with the electron density for undoped crystals, thus indicating t he disorder in the positions of the Nd and Ce atoms.