[1] Peking Univ, Coll Chem & Mol Engn, State Key Lab Struct Chem Unstable & Stable Speci, CNST,BNLMS, Beijing 100871, Peoples R China
[2] MIT, Dept Mat Sci, Cambridge, MA 02139 USA
[3] MIT, Dept Elect Engn & Comp Sci, Cambridge, MA 02139 USA
[4] MIT, Dept Phys, Cambridge, MA 02139 USA