A COMPARISON OF A LIQUID CRYSTALS MIXTURES
BY SIMULATION

R. LUKAC and F.J.VESELY
Computational Physics Group
Institute of Experimental Physics
University of Vienna, Strudlhofgasse 4
A-1090 Vienna
E-mail:LUKAC@Pap.UniVie.AC.AT and
VES@Pap.UniVie.AC.AT

ABSTRACT

Liquid crystals (LQ), with their interesting optical properties, have an important place in electronic devices such as displays. There are many studies using continuum theory, but many open questions can be answered only in the framework of a microscopic description. Simulations on the molecular level are very promising, but require large amounts of CPU time, even on modern, powerful hardware. The first step in this direction were simulations with hard bodies (needles, spherocylinders, ellipsoids) [1], but in the last few years also soft-potential simulations have been used. The Gay-Berne Potential [2] is applied frequently, providing a good compromise between realism and easy parametrisation.

Our reference system consisted of molecules with length 3 [3]. To study mixtures, we added molecules of length 1.5 and 6.0, respectively. Studies of pure liquids [4] show that the shorter molecules do not build a smectic phase even at high density; on the other hand, the very long molecules have strong ordering tendencies. We present results on equimolar, $25\%$ and $75\%$ mixtures at temperatures (0.5, 0.75, 1.0, 1.25 and 1.5) for various densities. The structures are characterized using various pair correlation functions [5,6,7]. Also, direct visualisation of structures was used to observe the smectic layering occuring in some of the investigated systems.

REFERENCES:

1. M.P. Allen, G.T. Evans, D.Frenkel and B.M.Mulder, Adv. Chem.Phys., 86, 1, (1993)
2. J.G.Gay and B.J.Berne, J.Chem.Phys., 74, 3316, (1981)
3. G.R.Luckhurst, R.A.Stephens and R.W.Phippen, Liq. Crystals, 8, 451, (1990)
4. E. de Miguel, L.F.Rull and K.E.Gubbins, Physica A, 177, 174, (1991)
5. G.R. Luckhurst and C.A.Veracini: The Molecular Dynamics of Liquid Crystals. (Kluwer Academic Publishers, Dordrecht, (1994))
6. F.J.Vesely: Computational Physics. An Introduction. (Plenum Press, London/New York, (1995))
7. M.P.Allen and D.J.Tildesley: Computer Simulation of Liquids. (Oxford University Press, Oxford, (1990))

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