1. Institute of PhysicsChinese Academy of Sciences Beijing 100190 China
2. School of physical sciencesUniversity of Chinese Academy of Sciences Beijing 100049 China
3. Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China
4. Neutron Scattering DivisionOak Ridge National Laboratory Oak Ridge TN 37831 USA
5. Shanghai Synchrotron Radiation Facility Shanghai 201204 China
6. Advanced Light SourceLawrence Berkeley National Laboratory Berkeley CA 94720 USA