A MOLECULAR-DYNAMICS STUDY OF A BI-DISPERSE LIQUID-CRYSTAL MIXTURE USING A GENERALIZED GAY-BERNE POTENTIAL

We report results from a constant NVE molecular dynamics simulation of a 50:50 mixture of Gay-Berne rods with axial ratios of 35 to 1 and 3 to 1. The simulation makes use of a recently developed extension of th e Gay-Berne potential which allows simulation of non-equivalent anisot ropic molecules with attractive interactions. There is clear evidence of pre-smectic ordering in the nematic phase. The system undergoes a w ell defined transition from the nematic phase to a randomly mixed smec tic phase. There is some local compositional ordering within the smect ic layers but no evidence of demixing. In both the nematic and smectic phases it is found that the longer molecules have a higher [S] order parameter than the shorter molecules. This difference in order paramet er is at its greatest a little below the isotropic-nematic transition temperature and decreases as the smectic phase is approached.