Local structural disorder

Though much of the HETCOR data bear out the details of the simulated unit cell, it differs in that the unit cell su ests that the PC7 iBM handles are at a 180° away from the polymer backbone. The fact that the 2D HETCOR suggests the existence of an orientation that is opposite to this shows the ability of the technique to provide direct proof of the intrinsic local structural disorder that is present in the system. The authors surest that this orientational disorder may result in disrupting the ID fijUerene channels and thus decrease the electron transport efficiency in these pathways. 

With increasing CP ionization, increasing chain mobility and the disordering of the local structure, the saturation of CP with protein in all cases becomes... 

Table 8.53 shows the main features of XAS. The advantages of EXAFS over diffraction methods are that the technique does not depend on long-range order, hence it can always be used to study local environments in amorphous (and crystalline) solids and liquids it is atom specific and can be sensitive to low concentrations of the target atom (about 100 ppm). XAS provides information on interatomic distances, coordination numbers, atom types and structural disorder and oxidation state by inference. Accuracy is 1-2% for interatomic distances, and 10-25 % for coordination numbers. 

All the disorder-specific depletions except one are, from the leftmost, typically buried amino acids. The one exception, N, is out of place in being both a surface-preferring and an order-promoting residue. Perhaps the short side chain, with its propensity to hydrogen-bond to the backbone (Presta and Rose, 1988 Richardson and Richardson, 1988), tends to induce local structure. This order-inducing tendency might explain the out-of-place behavior of N. 

The EXAFS, which occurs at higher energies above the edge, is due to the interference between the outgoing and the backscattered photoelectron waves (10-14). EXAFS provides information about the local structure of the x-ray absorbing atom. Typically, nearest neighbor bond lengths and coordination numbers can be determined to 0.02 A (1%) and one atom in four (25%) (4 ). The accuracy of these determinations is somewhat worse for outer-shell atoms, for disordered systems, or for systems with asymmetric distributions of atoms within a shell (15,16). 

In addition, many of the ferroelectric solids are mixed ions systems, or alloys, for which local disorder influences the properties. The effect of disorder is most pronounced in the relaxor ferroelectrics, which show glassy ferroelectric behavior with diffuse phase transition [1]. In this chapter we focus on the effect of local disorder on the ferroelectric solids including the relaxor ferroelectrics. As the means of studying the local structure and dynamics we rely mainly on neutron scattering methods coupled with the real-space pair-density function (PDF) analysis. 

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