1. Department of Chemistry, University of Washington 1 , Seattle, Washington 98195, USA
2. Department of Chemistry, University of Illinois at Urbana-Champaign 2 , Urbana, Illinois 61801, USA
3. Advanced Computing, Mathematics and Data Division, Pacific Northwest National Laboratory 3 , Richland, Washington 99352, USA
4. Department of Chemistry and Ames Laboratory, Iowa State University 4 , Ames, Iowa 50011, USA