1. Institute of Chemical Materials China Academy of Engineering Physics Mianyang Sichuan 621900 P. R. China
2. Sichuan Research Center of New Materials Chengdu Sichuan 610200 P. R. China
3. College of Materials Science and Engineering Hunan University Changsha Hunan 410082 P. R. China
4. Chemical Sciences and Engineering Division Argonne National Laboratory Argonne IL 60439 USA