Chevron Layer Structure in the Smectic A Phase of 8CB

Abstract

The smectic A layer structure of a homogeneously aligned 8CB liquid crystal (25 µm in thickness) has been studied by X-ray diffraction analysis. Contrary to the common recognition, it is found, for the first time, that the local layer structure of this type of cell changes to a chevron layer structure from a book-shelf structure, as the temperature decreases away from the N-S_A phase transition point. The formation of the chevron layer structure is also recognized by the characteristic defects: zig-zag defects appear as a boundary of two opposite chevron structures with focal conics.