1. Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973-5000, and Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973-5000