Disorder planar

Finding polariton states in disordered planar microcavities microscopically is a difficult task which do not attempt here. As a first excursion into the study of disorder effects on polariton dynamics, here we will follow (32) to explore the dynamics in a simpler microscopic model of a ID microcavity. Such microcavities are interesting in themselves and can have experimental realizations from the results known in the theory of disordered systems (39) one can also anticipate that certain qualitative features may be common for ID and 2D systems (38). 

From a theoretical point of view, Cui and Kertesz have studied the geometrical and electronic structures of PT and PMeT by energy-band theory where a screw axis of symmetry has been taken into account [68]. These authors confirm that the anti (rod) structure is slighltly more stable for PT while the syn (coil) conformation is preferred for PMeT. Finally, Ferro et al. applied molecular mechanics to obtain a monoclinic model of crystalline PT [84]. Their calculations show the weak dependence of packing energy on the unit cell parameter / , i.e. on the relative length of adjacent PT chains, in agreement with centro-symmetric and translation-ally disordered planar chains. 

Poly(vinylidene fluoride) Constitutional disorder Planar zig-zag XRl.CA 29... 

Progress in deducing more structural details of these fibers has instead been achieved using NMR, electron microscopy and electron diffraction. These studies reveal that the fibers contain small microcrystals of ordered regions of the polypeptide chains interspersed in a matrix of less ordered or disordered regions of the chains (Eigure 14.9). The microcrystals comprise about 30% of the protein in the fibers, are arranged in p sheets, are 70 to 100 nanometers in size, and contain trace amounts of calcium ions. It is not yet established if the p sheets are planar or twisted as proposed for the amyloid fibril discussed in the previous section. 

Inspection of Fig. 14(a) reveals that Ap > 0 in the corner while Ap < 0 at the tip. The positive deviation indicates that the two walls forming the wedge squeeze the hard spheres into the corner this effect is more pronounced for smaller values of 7. Around a tip, on the other hand, the hard spheres are spatially less constrained so that the fluid is more disordered, as in the corresponding planar case, so that Ap < 0. 

The basic building block of carbon is a planar sheet of carbon atoms arranged in a honeycomb structure (called graphene or basal plane). These carbon sheets are stacked in an ordered or disordered manner to form crystallites. Each crystallite has two different edge sites (Fig. 2) the armchair and zig-zag sites. In graphite and other ordered carbons, these edge sites are actually the crystallite planes, while in disordered soft and hard carbons these sites, as a result of turbostratic disorder, may not... 

This kind of disorder is present, for instance in the hexagonal form of s-PS. The disorder present in the so-called a modification [27,28], would correspond, in fact, to the statistical occurrence of two specific orientations of triplets of tram-planar chains, which leave unaltered the positions of the barycenters of the phenyl rings (Fig. 14) at well-defined positions in the 3-D lattice. 

The thiepin 13 (X = S) was found to be inert toward catalytic hydrogenation. The authors ascribe the stability of 13 (X = S) to a contribution of the charge-separated structures 13a and 13 b to the ground state of 13 (X = S) 71). An X-ray structural determination showed that 13 (X = S) is nearly planar with a disordered crystal structure similar to that of azulene 73). 

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