1. Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, United States
2. Theoretical and Applied Mechanics Program, Northwestern University, Evanston, Illinois 60208, United States
3. Alcorix Company, Plainfield, Illinois 60544, United States
4. Center for Nanoscale Materials, Argonne National Laboratories, Argonne, Illinois 60439, United States
5. Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States