1. National Center for Computational Sciences, Oak Ridge National Laboratory 1 , Oak Ridge, Tennessee 37831-6373, USA
2. Department of Chemistry and Biochemistry, University of Alabama 2 , Tuscaloosa, Alabama 35487-0336, USA
3. Department of Chemistry, Iowa State University 3 , Ames, Iowa 50011-2416, USA
4. Chemical and Biological Sciences Division, Ames National Laboratory 4 , Ames, Iowa 50011-2416, USA
5. RIKEN Center for Computational Science 5 , Kobe, Hyogo 650-0047, Japan