1. School of Materials Science and Physics, China University of Mining and Technology, Xuzhou 221116, P.R. China
2. Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, P.R. China
3. Computational Science Center, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea