With increasing computer power simulations take an important place also
in the investigation of liquid crystals (LQ). In the eighties, there were done many experiments
with hard body systems (ellipsoid, spherocylinder, needles), but in recent years
the Gay-Berne Potetial has become something like a standard soft potential for LQ's.
We investigate the influence of the elongation parameter on
the orientational phase transition of the Gay-Berne system. Results
of Monte Carlo simulations on 512 particles are given. Systems with
elongations 2, 2.5, 3, 3.5 and 4 were carefully compressed; results
include various correlation functions, the order parameter and
thermodynamic quantities.
At low temperature the pressure vs. density graph shows a
Van der Waals loop. From the oscillation of the
longitudinal pair correlation functions we can deduce the presence
of a isotropic - smectic transition.
As may be expected, short molecules do not have any orientational order
even at high density, while with increasing elongation the ordering tendency
becomes much more pronounced.
REFERENCES:
1. J.G.Gay and B.J.Berne, J.Chem.Phys., 74, 3316, (1981)
2. G.R.Luckhurst, R.A.Stephens and R.W.Phippen, Liq. Crystals, 8, 451, (1990)
3. G.R. Luckhurst and C.A.Veracini: The Molecular Dynamics of Liquid Crystals.
(Kluwer Academic Publishers, Dordrecht, (1994))
4. F.J.Vesely: Computational Physics. An Introduction.
(Plenum Press, London/New York, (1995))
5. M.P.Allen and D.J.Tildesley: Computer Simulation of Liquids.
(Oxford University Press, Oxford, (1990))
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