Local structure in nematic and isotropic liquid crystals

TL;DR

This study uses computer simulations to analyze how the phase transition affects the direct correlation functions in anisotropic fluids, revealing that nematic phases break rotational symmetry in the DCF.

Contribution

It provides a detailed, approximation-free analysis of the DCF in nematic and isotropic liquid crystals, highlighting symmetry-breaking effects.

Findings

Symmetry-breaking contributions to DCF emerge in nematic phase.

In isotropic phase, DCF agrees with Percus-Yevick theory.

Diverse contributions to DCF are distinguished using a molecular-fixed reference frame.

Abstract

By computer simulations of systems of ellipsoids, we study the influence of the isotropic/nematic phase transition on the direct correlation functions (DCF) in anisotropic fluids. The DCF is determined from the pair distribution function by solving the full Ornstein-Zernike equation, without any approximations. Using a suitable molecular-fixed reference frame, we can distinguish between two qualitatively different contributions to the DCF: One which preserves rotational invariance, and one which breaks it and vanishes in the isotropic phase. We find that the symmetry preserving contribution is barely affected by the phase transition. However, symmetry breaking contributions emerge in the nematic phase and may become quite substantial. Thus the DCF in a nematic fluid is not rotationally invariant. In the isotropic fluid, the DCF is in good agreement with the prediction of the Percus-Yevick theory.