1. School of Materials Science and Engineering Nanyang Technological University Singapore 639798 Singapore
2. Department of Chemistry Northwestern University Evanston IL 60208 USA
3. Materials and Structure Laboratory Tokyo Institute of Technology Yokohama 226‐8503 Japan
4. Department of Physics and Astronomy University of Padova Padova I‐35131 Italy
5. Department of Computer Science University of Verona Italy University of Verona Ca’ Vignal 2, Strada le Grazie 15 Verona I‐37134 Italy
6. Institute of Materials Research and Engineering A*STAR Agency for Science Technology and Research Singapore 138634 Singapore
7. Department of Physics Southern University of Science and Technology Shenzhen 518055 China