UNIVERSALITY IN THE FAST ORIENTATIONAL RELAXATION NEAR ISOTROPIC-NEMATIC TRANSITION

Detailed molecular dynamics simulations of Lennard-Jones ellipsoids ha ve been carried out to investigate the emergence of criticality in the single-particle orientational relaxation near the isotropic-nematic ( IN) phase transition. The simulations show a sudden appearance of a po wer-law behavior in the decay of the second-rank orientational relaxat ion as the IN transition is approached. The simulated value of the pow er-law exponent is 0.56, which is larger than the mean-field value (0. 5) but less than the observed value (0.63) and may be due to the finit e size of the simulated system. The decay of the first-rank orientatio nal time correlation function, on the other hand, is nearly exponentia l but its decay becomes very slow near the isotropic-nematic transitio n, The zero-frequency rotational friction, calculated from the simulat ed angular Velocity correlation function, shows a marked increase near the IN transition. (C) 1998 American Institute of Physics. [S0021-960 6(98)52541-X].