COMMUNICATIONS Single particle and collective orientational relaxation in an anisotropic liquid near the isotropic–nematic transition

We report molecular dynamics simulation results for the single particle and collective orientational correlations for Gay–Berne fluid of anisotropy parameters k53 and k855. The following significant results are reported. ~i! The decay of collective orientational relaxation of rank two is found to slow down appreciably while approaching the isotropic–nematic ~I–N! transition. It eventually becomes even slower than the single particle orientational relaxation of rank one. Surprisingly, even the latter shows a marked slowing down near the I–N transition. ~ii! Analysis of the long-time behavior shows a breakdown of the rank dependence predicted by the Debye law in the same region. ~iii! An analysis of the memory functions of the orientational time-correlation functions shows that for the collective relaxation surprisingly approaches a Markovian behavior near the I–N transition. © 1997 American Institute of Physics. @S0021-9606~97!51403-6# LETTERS TO THE EDITOR