1. State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong University Xi'an 710049 P. R. China
2. Department of Physics Chalmers University of Technology Göteborg SE 41296 Sweden
3. Department of Energy Conversion and Storage Technical University of Denmark Kgs. Lyngby 2800 Denmark
4. College of Aerospace Science and Engineering National University of Defense Technology Changsha Hunan 410073 P. R. China