Crystallographical distortion

Moreover, point defects will undoubtedly cause significant crystallographic distortions in the region of the affected site, which endow the defects with a... 

Table 2. Crystallographical distortion and continuity for crystalline and crystallized monolayer.

Table 3.Crystallographical distortion and continuity of stearic acid monolayer prepared by multi-step creep method and continuous compression method. 

Preparation method (Stearic acid Tsp = 293 K) Crystallographical distortion, Dial /% Crystallographical continuity, Liat / nm... 

It is well established that all the known martensitic transitions, before Nitinol, occurs through crystallographic transformation [11], As described above [10], single crystal X-ray diffraction work shows a crystallographic distortion (rather than transformation) and therefore is a second-order transformation [12], This conclusion has the support of heat capacity investigation [13] that gave a latent heat of transition AH >... 

The theoretical treatment of a solid-state transition involving covalent (localized) vs. conduction (delocalized) electronic transformation was first enunciated by Mott [44], By considering the Pauli Exclusion Principle and the electron-electron interaction during the transformation, it was shown that such transition will be critically dependent upon the inter-atomic distances. The number of electrons already existing in the conduction state will in turn influence the critical inter-atomic distances and the transition therefore, it is necessarily a cooperative phenomenon. Later, in a theoretical treatment of the same subject, but based on a different context, Goodenough [45] has shown that the transition is likely to be second-order if the number of electrons per like atom is non-integral. Further, a crystallographic distortion is a prominent manifestation of such a transition. 

The break down of usual concepts of spin gap formation can be studied very well in the recently established Tr3 1 systems MgTi204 [56], TiOCl [57] or NaTiSi206 [58], In all these compounds a crystallographic distortion is accompanied with the formation of an unusually large spin gap and strong fluctuations exist, pointing to electronic energy scales involved. 

Even smaller but still measurable changes (typically 2 ppm) in the Si chemical shifts result from the presence of crystallographic distortions in Si environments which are otherwise similar, for example, the Q (3A1) site in the mineral natrolite (- 87.7 ppm) which beomes — 86.3 and — 89.1 in the distorted sites of scolecite (Table 4.1). Thus, the Si chemical shifts can provide information about a considerable range of perturbations in the Si environment. 

In 1953, Williamson and Hall [WIL 53] snggested a simple method for solving this problem. It works by considering that both the limited size of the ciystals and the presence of crystallographic distortions lead to Lorentzian intensity distributions. 

It also produces a substantial quadrupole splitting as seen in Fig. 6.5. This implies that a substantial crystallographic distortion is induced. The rather broad room-temperature spectrum was believed to be the result of stresses created during formation of the absorber pellet. These high-pressure data for KFeFs were used by Simdnek and Wong as already discussed in Chapter 5 (p. 95) to calculate a value of dR/R for the 14 41-keV transition. 

The observed angular dependence of AH is not simply related to the angular dependence of the anisotropy energy. The existence of domains and of crystallographic distortions in the volume of the domain walls could cause two-magnon disorder scattering and, hence, further anisotropic contributions to the linewidth [6]. 

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