Analysis of the shape of x-ray diffraction peaks originating from the hexatic phase of liquid crystal films

TL;DR

This study investigates the shape of x-ray diffraction peaks from the hexatic phase of liquid crystal films, analyzing temperature-dependent profiles and comparing experimental results with theoretical models.

Contribution

It provides a detailed analysis of diffraction peak shapes in the hexatic phase and validates theoretical predictions with experimental data.

Findings

Near the transition, peaks are Gaussian-shaped.

At lower temperatures, peaks are better fitted by Voigt functions.

Theoretical estimations agree with experimental results.

Abstract

X-ray diffraction studies of the bond-orientational order in the hexatic-B phase of 75OBC and 3(10)OBC compounds are presented. The temperature evolution of an angular profile of a single diffraction peak is analyzed. Close to the hexatic-B-smectic-A transition these profiles can be approximated by the Gaussian function. At lower temperatures in the hexatic-B phase the profiles are better fitted by the Voigt function. Theoretical analysis of the width of diffraction peaks in three-dimentional (3D) hexatics is performed on the basis of the effective Hamiltonian introduced by Aharony and Kardar. Theoretical estimations are in good agreement with the results of x-ray experiments.