X-ray cross-correlation analysis of liquid crystal membranes in the vicinity of hexatic-smectic phase transition

TL;DR

This study uses angular x-ray cross-correlation analysis to investigate the bond-orientational and positional order in liquid crystal membranes near the hexatic-smectic phase transition, revealing a strong coupling between these orders.

Contribution

It introduces the application of XCCA to directly measure bond-orientational order parameters and their temperature dependence in liquid crystal membranes near phase transition.

Findings

Larger correlation lengths for higher-order Fourier components of BO order.

Strong coupling between bond-orientational and positional order.

Temperature dependence of positional correlation lengths analyzed.

Abstract

We present an x-ray study of liquid crystal membranes in the vicinity of hexatic-smectic phase transition by means of angular x-ray cross-correlation analysis (XCCA). By applying two-point angular intensity cross-correlation functions to the measured series of diffraction patterns the parameters of bond-orientational (BO) order in hexatic phase were directly determined. The temperature dependence of the positional correlation lengths was analyzed as well. The obtained correlation lengths show larger values for the higher-order Fourier components of BO order. These findings indicate a strong coupling between BO and positional order that has not been studied in detail up to now.