1. Department of Physics University of Illinois at Urbana–Champaign Urbana IL 61801 USA
2. Department of Materials Science and Engineering University of Illinois at Urbana–Champaign Urbana IL 61801 USA
3. Materials Research Laboratory University of Illinois at Urbana–Champaign Urbana IL 61801 USA
4. National Center for Supercomputing Applications University of Illinois at Urbana–Champaign Urbana IL 61801 USA