Structure and freezing of a fluid of long elongated molecules

Abstract

We have used the density-functional theory to locate the freezing transitions and calculate the values of freezing parameters for a system of long elongated molecules which interact via the Gay-Berne pair potential. The pair correlation functions of isotropic phase which enter in the theory as input informations are found from the Percus-Yevick integral equation theory. At low temperatures the fluid freezes directly into the smectic A phase on increasing the density. The nematic phase is found to stabilize in between the isotropic and smectic A phases only at high temperatures and high densities. These features of the phase diagram are in good agreement with the computer simulation results.

Density functional theory of freezing of a system of conjugated oligomers parameterised via Gay–Berne potential

“…The phase diagrams shown in Figures 5 and 6 are qualitatively similar to the earlier computer simulation and theoretical studies on the system of mesogens of low aspect ratio interacting via GB potential. [18,19,28,31] …”

“…[23][24][25][26][27] In this paper, our objective is to study the liquid crystalline phase transitions and the topology of the phase diagram of a system of highly elongated (κ ' 10) model ellipsoidal conjugated oligomers using the density functional theory (DFT) of freezing. [28,29] Pair correlation functions needed as input information in DFT have been calculated using the Percus-Yevick (PY) integral equation theory at a grid of temperature and density. We present the results of the transition parameters corresponding to the isotropic-nematic, isotropic-smectic A and nematic-smectic A phase transitions.…”

“…Using the transition parameter obtained in our calculation, we have plotted the temperature-density and pressure-temperature phase diagrams which are found to be qualitatively similar to the one obtained in simulations for the systems with low aspect ratio GB particles. [18,19,28,31] The paper is organised as follows. In Section 2, we describe PY integral equation theory for the calculation of the pair correlation functions of the isotropic phase of the ellipsoidal conjugated oligomers.…”

An Integral Equation Approach to Orientational Phase Transitions in Quadrupolar Gay-Berne Fluid Using Density-Functional Theory

“…Note that for a uniaxial system consisting of cylindrically symmetric molecules m = n = 0 and, therefore, one has /7(r,£2) = /7"XEaexpO-G,.r)/^(cos^) / q (22) and 350…”

“…The first term in equation (7) represents the GB potential which is expressed by equation (1) and the second term is the potential due to the electrostatic interactions such as the quadrupolar-quadrupolar interaction, f/^^ [22],…”