1. State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology Beijing 100029 P. R. China
2. Key Laboratory of New Processing Technology for Nonferrous Metal & Materials Ministry of Education Guangxi Key Laboratory of Optical and Electronic Materials and Devices Guilin University of Technology Guilin 541004 P. R. China
3. Institute of Physics Chinese Academy of Sciences Dongguan Neutron Science Center Beijing 100190 Dongguan 523803 P. R. China
4. Deutsches Elektronen-Synchrotron DESY Notkestr 85 22607 Hamburg Germany
5. Inorganic Chemistry Laboratory University of Oxford Oxford OX1 3QR UK