Chapter

Chapter 4.4 Scattering from mesomorphic structures

Reciprocal space

First Online Edition (2006)

Part 4. Diffuse scattering and related topics

  1. P. S. Pershan

Published Online: 1 JAN 2006

DOI: 10.1107/97809553602060000566

International Tables for Crystallography

International Tables for Crystallography

How to Cite

Pershan, P. S. 2006. Scattering from mesomorphic structures. International Tables for Crystallography. B:4:4.4:449–465.

Author Information

  1. Division of Engineering and Applied Science and The Physics Department, Harvard University, Cambridge, MA 02138, USA

Publication History

  1. Published Online: 1 JAN 2006

Abstract

The terms mesomorphic and liquid-crystalline are used synonymously. The order of mesomorphic phases is intermediate between that of liquids and crystals. The progression from the completely symmetric isotropic liquid through the mesomorphic phases into the crystalline phases can be described in terms of three separate types of order. The first kind, molecular orientational order, results from the molecules having some preferential orientation, as found in nematic phases. The second type of order is referred to as bond orientational order and the third kind of order is a positional order of an indefinite lattice of the type that defines the 230 space groups of conventional crystals. For mesomorphic phases with a layered structure, this positional order can be separated into positional order along the layer normal and perpendicular to it, or within the layers. In this chapter, mesomorphic phases are classified according to the different kinds of order present and the scattering from each kind of phase is described. Discotic and other kinds of mesomorphic structures are also discussed.

Keywords:

  • scattering;
  • scattering cross sections;
  • mesomorphic structures;
  • liquid crystals;
  • nematic phases;
  • smectic-A phases;
  • smectic-C phases;
  • smectic-B phases;
  • smectic-D phases;
  • hexatic phases;
  • smectic-F phases;
  • smectic-I phases;
  • crystal-E phases;
  • crystal-G phases;
  • crystal-H phases;
  • crystal-J phases;
  • crystal-K phases;
  • crystal-B phases;
  • discotic phases;
  • herringbone packing;
  • molecular rotation;
  • molecular orientational order;
  • bond orientational order;
  • quasi-long-range order;
  • surface effects