Analysis of the shape of x-ray diffraction peaks originating from the   hexatic phase of liquid crystal films
  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. 
I. A. Zaluzhnyy, R. P. Kurta, A. P. Menushenkov, B. I. Ostrovskii, and   I. A. Vartanyants
cond-mat.soft