1. Mathematics and Computer Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
2. Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
3. Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
4. Northwestern-Argonne Institute for Science and Engineering, Evanston, Illinois 60208, USA
5. Departmento de Materiales, Universidad Nacional de Colombia, Sede Medellin, Colombia