Crystal mosaicity

For purposes of display, the intensity of each calculated reflection was assumed to be distributed about its mean position according to Gaussian distributions in 20 and p. The breadths of these distributions represent the expected peak broadening due to finite crystallite sizes, the crystal mosaic, and paracrystal distortions, which are not available a priori from the model calculations. Additionally, we require an estimate for p1/2 for the Lorentz correction of meridional reflection intensities. The peak broadening distributions were selected of the form... 

A protein crystal mosaicity in the 0.1 mrad (0.006°) range is required if the long crystal to plate distances are to be realised. As documented by Helliwell (1988) and Colapietro, Helliwell, Thompson and Spagna (unpublished work) protein crystals at room temperature do have rocking widths of 0.01-0.02° (0.17-0.34 mrad) FWHM. 

Fig. 3 Top Transmission spectrum recorded at 1.77 K on a single crystals mosaic of Mni2Ac with the crystallographic c-axis (easy axis) parallel to the radiation propagation direction, using parallel polarizer and analyzer. Bottom Frequency dependence of the Faraday rotation, derived from the transmission spectrum. Adapted from [84]...

The case of a mixed dimerized stack system is well exemplified by the room temperature infrared spectra of M2P-TCNQ (M2P = N,N-dimethyl-phenazine). The polarized reflectance spectra of a single crystal mosaic (Fig. 6a) are dominated by bands whose polarization is parallel to that of the CT band observed around 5000 cm . The assignment of these bands to vibronic effects,related to totally symmetric modes of both the donor and the acceptor, is given in Table IV. 

However, possible extrinsic sources of line broadening, such as strain effects and crystal mosaicity, must be carefully ruled out before any interpretation of single-crystal measurements is attempted. Finally, it must be noted that the very fast sweeping rates typical of pulsed-field experiments may lead to thermal nonequilibrium conditions at the crossovers. In this case, the observed lineshape is also strongly influenced by magnetocaloric effects. ... 

Fig. 4-9. This diagram shows the intensity variation with angle for a rock salt crystal in the region near the Bragg angle, 0q, for an incident monochromatic beam. The area under the mosaic crystal curve could be thirty times greater than the ideal. (After Renninger, Z. Krist. 89, 344.)...

A considerable amount of research has been conducted on the decomposition and deflagration of ammonium perchlorate with and without additives. The normal thermal decomposition of pure ammonium perchlorate involves, simultaneously, an endothermic dissociative sublimation of the mosaic crystals to gaseous perchloric acid and ammonia and an exothermic solid-phase decomposition of the intermosaic material. Although not much is presently known about the nature of the solid-phase reactions, investigations at subatmospheric and atmospheric pressures have provided some information on possible mechanisms. When ammonium perchlorate is heated, there are three competing reactions which can be defined (1) the low-temperature reaction, (2) the high-temperature reaction, and (3) sublimation (B9). 

For density values g > 0.92 g/cm3 the deformation modes of the crystals predominate. The hard elements are the lamellae. The mechanical properties are primarily determined by the large anisotropy of molecular forces. The mosaic structure of blocks introduces a specific weakness element which permits chain slip to proceed faster at the block boundaries than inside the blocks. The weakest element of the solid is the surface layer between adjacent lamellae, containing chain folds, free chain ends, tie molecules, etc. 

The integrated intensity of reflection of an X-ray line from an extended face of a mosaic crystal is4)... 

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