[1] Penn State Univ, Dept Phys, University Pk, PA 16802 USA
[2] Penn State Univ, Mat Res Inst, University Pk, PA 16802 USA
[3] Univ Minnesota, Dept Chem Engn & Mat Sci, Minneapolis, MN 55455 USA
[4] Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA
[5] Los Alamos Natl Lab, Ctr Nonlinear Studies, Los Alamos, NM 87545 USA