Abstract
We investigate the density of vibrational states g(ω) for 6000 atom polymer particles involving all 18,000 degrees of freedom. The particles are efficiently generated using a molecular dynamics-based computational algorithm and a molecular mechanics method. The density of states spectrum g(ω) clearly shows two distinguishable frequency regions in the polymer system: high (760<ω<1240 cm-1) and low (0<ω<350 cm-1) frequency modes. By calculating the level-spacing distributions, we find the distribution of the low eigen-frequency corresponds to that of a Wigner distribution. In contrast, Poisson behavior is found for the high frequency region. The eigenvectors for the two regions are analyzed by using a random walk method and Stewart's perturbation theory, both indicate random character for the eigenvectors of the low frequency modes. The random character of the eigenvectors should have ramifications to most types of spectroscopy since transformations of the transition operator to random normal coordinates will cause a widespread mixing, i.e., no selection rules.
| Original language | English |
|---|---|
| Pages (from-to) | 191-196 |
| Number of pages | 6 |
| Journal | Computational and Theoretical Polymer Science |
| Volume | 11 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jun 2001 |
Funding
K.F. is supported by the Postdoctoral Research Associates Program administered jointly by fellowship at Oak Ridge National Laboratory (ORNL) and Oak Ridge Institute for Science and Education. C.Y. was supported by a Householder fellowship at ORNL. Research sponsored by the Division of Materials Sciences, Office of Basic Energy Sciences, and Applied Mathematical Science Program, Office of Science, US Department of Energy under contract DE-AC05-96OR22464 with Lockheed-Martin Energy Research Corporation.