Bragg reflexes

Coming back to the detailed analysis of diffraction patterns, we note that such efforts can be in practice more complicated for real samples for different reasons. First of all, the crystallites (grains) inside a polycrystalline sample might have a preferred orientation (texture), and accordingly, the Bragg reflexes of all other orientations are extremely suppressed in their intensity compared to those expected from calculated structure factors. Such a behavior can be expected e.g. in the case of epitaxially grown thin films that adopt the structure or at least the orientation of the substrate. This is observed e.g. for the passive films on iron discussed above [4], and in part also for those on Ni [19] but also for electrodeposited metal films. 

For collapsed SmS the determination of the degree of intermediate valence has long been disputed in literature and mostly been taken from the lattice constant of chemically collapsed SmS. However, Batlogg et al. (1976b) have performed a differential Bragg reflex measurement between semiconducting and pressurized SmS and found a lattice constant of 5.68 A from which a valence mixing of 2.85 can be obtained. 

For comparison of structural aspects the set binders have been characterized by X-ray diffiac-tion (XRD). Figure 6 proves for the type A binder, an amorphous structure to a large extent, and for the B type binder pronounced crystalline features by sharp Bragg reflexes. 

Luck, W. Klier, M. Wesslau, H. Uber Bragg-Reflexe mit sichtbarem licht an monodispersen kunstst-offlatices. 1. Berichte der Bunsen-geseUschaft fur. Phys. Chem. 1963, 67, 75-83. 

Theoretical moduli of elasticity calculated in this way are largely confirmed experimentally by what are known as lattice moduli, or crystal moduli. The lattice moduli are determined by following the Bragg angle of selected reflexes by X-ray crystallography as a function of applied stress. The apparent lattice modulus so obtained ... 

According to Bragg s law the positions of WAXS reflexes refer to the distance between crystalline planes within the crystallites. In the compression moulded as well as in the injection moulded plates a couple of crystalline reflexes could be identified. The reflexes with the highest intensity within the relevant angular region are summarised in table 1. 

ID-Monolayer Polymesomorphism. DSC scans show that a number of PMCS-6 exhibit a polymesomorphic transition II-> I within the temperature region of ID-mesophase existence (Table II). As a rule for atactic non-crystallizible PMCS-6, the X-ray diffraction patterns obtained below T i reveal no additional Bragg reflections besides the principal reflex at 20. While the parameter d shows systematic linear increase with the temperature due to the thermal expansion, the slope in the plot 20 1 vs. T experiences a change just near Tu, j. A similar... 

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