Effect of the varying repulsive core of Gay–Berne pair potential on the structure and freezing transition in a two-dimensional system of soft ellipses

ABSTRACT

We have investigated the effect of the strength of repulsive core of Gay–Berne (GB) ($\mathit{n}-6$) pair potential on the pair correlations and isotropic-nematic ($\mathit{I}-\mathit{N}$) freezing transition in a system of soft ellipses confined to a two-dimensional plane. The power $\mathit{n}$ has been varied in the range $8\le \mathit{n}\le 16$ at an interval of two. Percus–Yevick (PY) integral equation theory (IET) has been solved to calculate the pair correlations of the isotropic fluid, which has been then used in the density functional theory to determine the isotropic-nematic transition parameters. The pair correlations obtained by PY theory have been compared with those obtained by NVT Monte-Carlo (MC) simulation. We observe a better agreement between PY and MC correlations at lower $\mathit{n}$-values of the interaction potential. An increase in the values of $\mathit{n}$ results in more intricate structures manifested in both the radial distribution part and the higher order correlations. The $\mathit{I}-\mathit{N}$ transition parameters are found to be sensitive to the value of the exponent $\mathit{n}$. The transition density is found to decrease, whereas the corresponding orientational order parameter is found to increase with the increase in $\mathit{n}$ for a given temperature. At a given temperature, we observe a cut-off of $\mathit{n}$, below which the nematic does not stabilise. The smaller value of change in density at the transition indicates that the $\mathit{I}-\mathit{N}$ transition is of weakly first order.

Graphical abstract

KEYWORDS:

• Monte-Carlo simulation
• integral equation theory
• Integral Equation Theory
• density functional theory
• Density Functional Theory
• Gay-Berne potential
• isotropic-nematic transition

Acknowledgments

The Authors would like to thank Prof. Y. Singh and Prof. J. Ram for many helpful discussions.

Disclosure statement

No potential conflict of interest was reported by the author(s).