Abstract
Molecular dynamics simulations have been performed to investigate the rotational motion in the nematic and isotropic phases of a model mesogenic system in which the interactions between the molecules are represented by the Gay-Berne potential. First-rank end-over-end rotational relaxation times, analogous to those measured using dielectric relaxation spectroscopy for real mesogens with a longitudinal electric dipole, have been determined as a function of temperature and density. The relaxation times at temperatures throughout the nematic region are found to be larger than the values extrapolated from the isotropic phase to the same temperature. The simulation results are compared with the extended Debye theory for dielectric relaxation in the nematic phase. This relates the reduction in the relaxation rate to the retardation factor which depends on the Maier-Saupe strength parameter, and in turn is defined uniquely by the second-rank orientational order parameter. The simulations indicate that the retardation factor at constant strength parameter is density dependent, a feature neglected in the relaxation theory. We compare the simulation results where possible with experiment.
| Original language | English |
|---|---|
| Pages (from-to) | 1365-1371 |
| Number of pages | 7 |
| Journal | Journal of Physics B: Atomic, Molecular and Optical Physics |
| Volume | 99 |
| Issue number | 16 |
| Publication status | Published - Aug 2001 |
Keywords
- HIGH-PRESSURE
- COMPUTER-SIMULATION
- ANISOTROPIC SYSTEMS
- ORDER-PARAMETER
- LIQUID-CRYSTALS
- PHASE