1. Materials Theory Division, Department
of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
2. Department
of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
3. School
of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore
4. Energy Research Institute @NTU (ERI@N), Research Techno Plaza, X-Frontier Block, Level 5, 50 Nanyang Drive, Singapore 637553, Singapore