Eur. Phys. J. E (2005) 17: 345-351
https://doi.org/10.1140/epje/i2005-10014-x

Original Article

Effect of shape anisotropy on the phase diagram of the Gay-Berne fluid

Department of Physics, Banaras Hindu University, 221 005, Varanasi, India

^* e-mail: mpankajg@yahoo.com
^** e-mail: jram@bhu.ac.in

Received: 22 March 2005
Accepted: 22 April 2005
Published online: 11 July 2005

Abstract

We have used the density functional theory to study the effect of molecular elongation on the isotropic-nematic, isotropic-smectic A and nematic-smectic A phase transitions of a fluid of molecules interacting via the Gay-Berne intermolecular potential. We have considered a range of length-to-width parameter 3.0 ⩽ x ₀ ⩽ 4.0 in steps of 0.2 at different densities and temperatures. Pair correlation functions needed as input information in density functional theory are calculated using the Percus-Yevick integral equation theory. Within the small range of elongation, the phase diagram shows significant changes. The fluid at low temperature is found to freeze directly from isotropic to smectic A phase for all the values of x₀ considered by us on increasing the density while the nematic phase stabilizes in between isotropic and smectic A phases only at high temperatures and densities. Both isotropic-nematic and nematic-smectic A transition density and pressure are found to decrease as we increase x₀. The phase diagram obtained is compared with computer simulation result of the same model potential and is found to be in good qualitative agreement.