(Received: October 7, 2005; Accepted for publication: April 27, 2006; Published on Web: July 18, 2006)
The end-over-end rotational motion of nematic-phase molecules was examined by an isobaric-isothermal molecular-dynamics simulation for a Gay-Berne mesogenic system. The result was compared with the Meier-Saupe theory and the previous result obtained from a molecular-dynamics simulation for the same Gay-Berne model at constant volume in order to examine the influence of volume fluctuation on nematic-phase dynamics. The results from the simulation at constant pressure were closer to the theoretical value the retardation factor g||, which is the concept used to interpret reduction of the relaxation time for end-over-end rotational molecular motion, throughout the entire range of the second-rank orientational order parameter <P2> and the strength parameter of Maier-Saupe form s than were those values for constant volume. Volume fluctuation is important in evaluating the retardation factor g||. This finding significantly increases our understanding of the role of pressure control in the simulation of slow dynamics in the liquid crystalline phase.
Keywords: Liquid crystal, Nematic phase, Molecular dynamics, Rotational dynamics, Retardation factor
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