[1] Stanford Univ, Dept Chem, Stanford, CA 94305 USA
[2] Stanford Univ, PULSE Inst, Stanford, CA 94305 USA
[3] SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA
[4] Georgia Inst Technol, Ctr Computat Mol Sci & Technol, Sch Chem & Biochem, Atlanta, GA 30332 USA