Chiral diffraction vector

Chiral supramolecular architectures are sometimes formed by molecules that stay achiral as a single entity. Hence, chirality arises just because of close-packed self-assembly on the surface. The single pentane molecule in its linear configuration remains achiral. For the close-packed monolayer, a rectangular unit cell has been identified by neutron diffraction. In addition, a tilt of the molecular axis with respect to the adlattice vectors would make the whole layer chiral [33]. For a particular mirror domain, the tilt angle i// can be either turned clockwise or counterclockwise (Fig. 12). 

Gao etal. have developed a quantitative structure determination technique of SWNT using NED. This, coupled with improved electron diffraction pattern quahty using NED, allows a determination of both the diameter and chiral angle, and thus the chhal vector (n, m), from individual SWNTs. The CNT they studied were grown by chemical vapor deposition (CVD). TEM observation was carried out in a JEOL201 OF TEM with a high voltage of 200 keV. 

The simplest case of Bragg diffraction is shown in Fig. 20 a for an ideal planar chiral nematic. If is the scattering vector, arising from the structure in, and local fluctuation of, e r), the dielectric tensor, then... 

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