X-ray diffraction powder methods

The formation of such materials may be monitored by several techniques. One of the most useful methods is and C-nmr spectroscopy where stable complexes in solution may give rise to characteristic shifts of signals relative to the uncomplexed species (43). Solution nmr spectroscopy has also been used to detect the presence of soHd inclusion compound (after dissolution) and to determine composition (host guest ratio) of the material. Infrared spectroscopy (126) and combustion analysis are further methods to study inclusion formation. For general screening purposes of soHd inclusion stmctures, the x-ray powder diffraction method is suitable (123). However, if detailed stmctures are requited, the single crystal x-ray diffraction method (127) has to be used. 

Arndt and Ahlers [38] used X-ray powder diffraction method for studying the influence of cations on the mode of action of miconazole on yeast cells. The influence of miconazole nitrate on yeast plasma membranes was studied in a concentration range of 0-100 pM. The reaction of 100 pM miconazole with the... 

Recent developments and prospects of X-ray powder diffraction methods. In the preceding paragraph a few comments have been made about diffractometry and its uses in the analysis of materials. However it is not possible to give here an account of this subject its principles and underlying theories, its experimental techniques and... 

X-ray powder diffraction methods have been used quite frequently for the limited purpose of finding out whether a series of lanthanide complexes is isomorphous. In most cases, the complexes with the same stoichiometry are isomorphous. X-ray powder patterns of the complexes of DPPA with lanthanide hexafluorophosphate (225), for example, are very similar and are consistent with the existence of only one iso-... 

TABLE 2.3 Summary of X-ray powder diffraction methods used to analyze clopidogrel bisulfate... 

Er-Zr-Sb. Morozkin and Sviridov (2001) investigated the crystal structure of the ErZrSb compound by using an X-ray powder diffraction method CeScSi structure type, a = 0.4204, c= 1.6159. 

R-U-Sb. A NaCl structure type was observed for continuous solid solution Yi HJxSb alloys, x = 0-1, a = 0.6165-0.6208 by using X-ray powder diffraction method (Frick et al.,... 

Wilson, M. J. (1987). X-ray powder diffraction methods, in A Handbook of Determinative Methods in Clay Mineralogy (M. J. Wilson, Ed.). Glasgow Blackie, 26-98. 

Smith DK, Johnson GG Jr, Scheible A, Wims AM, Johnson JL, Ullmann G. 1987. Quantitative X-ray powder diffraction method using the full diffraction pattern. Powder Diffr. 2(2) 73-77. 

In terms of the structural features that are probed with various analytical methods, solid state nuclear magnetic resonance (SSNMR) may be looked upon as representing a middle ground between IR spectroscopy and X-ray powder diffraction methods. The former provides a measure of essentially molecular parameters, mainly the strengths of bonds as represented by characteristic frequencies, while the latter reflect the periodic nature of the structure of the solid. For polymorphs differences in molecular environment and/or molecular conformation may be reflected in changes in the IR spectrum. The differences in crystal structure that define a polymorphic system are clearly reflected in changes in the X-ray powder diffraction. Details on changes in molecular conformation or in molecular environment can only be determined from full crystal structure analyses as discussed in Section 4.4. 

The x-ray powder diffraction method dates back to Debye and Scherrer who were the first to observe diffraction from LiF powder and succeeded in solving its crystal structure. Later, HulF suggested and Hanawalt, Rinn and FreveP formalized the approach enabling one to identify crystalline substances based on their powder diffraction patterns. Since that time the powder diffraction method has enjoyed enormous respect in both academia and industry as a technique that allows one to readily identify the substance both in a pure form and in a mixture in addition to its ability to provide information about the crystal structure (or the absence of crystallinity) of an unknown powder. 

Californium tribromide has been studied by spectroscopic and X-ray powder diffraction methods between 25 and 700 °C and was found to undergo thermal reduction to californium(ii) with increasing temperature. Despite this ingrowth of cali-fornium(ii) into californium tribromide, all the powder diffraction patterns showed the existence of only the monoclinic aluminium trichloride type structure of CfBr3. A mechanism which involved a reversible shift of electron density from the bromide ions to californium(iii) ions with temperature was postulated. Studies on the californium metal system have indicated the existence of both a bivalent and higher valence form. The use of or Es as dopants in strontium dichloride, and the temperature... 

Thermogravimetric and X-ray powder diffraction methods have revealed"" the dehydration of sodium aluminium alum to proceed by reactions (43)—(45). 

This definition is descriptive and still applicable. Today, x-ray powder diffraction methods are indispensable for describing new minerals. Without x-ray diffraction, synthetic zeolites would be hopelessly confused. All of the early attempts to synthesize zeolites are meaningless because x-ray diffraction data are not available. 

Mayer and Tassa (1969) and Mayer and Felner (1973) investigated the concentration section LaNi Si2 jt by means of X-ray powder diffraction methods. For x < 0.4 the ThSi2-type structure was claimed to be stable. LaNio4Si, crystallizes with the AlBj-type structure. In analogy to the X-ray data of the isotypic NdNiQ4Si, <, a statistical distribution of Ni,Si atoms at the 2d site of P6/mmm was assumed. 

Mayer and Eshdat (1968) studied the structural variation of the concentration section NdSi Gc2, by means of X-ray powder diffraction methods. Samples were prepared by direct reaction at 1500-1700 °C in a Ta boat under argon. The compacted mixture of 99.9% purity was heated for a few minutes in an induction furnace slightly above the melting point. 

Muravyova et al. (1971) and Muravyova (1972) investigated the phase relations near the Y-Si binary (isothermal section at 500°C for 0-33 a/o Y). Alloys were prepared by arc melting under argon, followed by heat treatment for 750 h at 500°C. 96 samples were analyzed by X-ray powder diffraction methods. Starting materials were Y 99.6%, Al 99.98% and Si 99.98%. 

Raman (1968) investigated combinations of ErSi (CrB-type, branch I, Cmcm) and GdNi (CrB-type, branch 11 Cmcm) by means of X-ray powder diffraction methods. No appreciable mutual solid solubility was observed. Powder diffraction patterns were said to be complex. For sample preparation and structural details, see Er-Al-Si,... 

X-ray diffraction also provides a convenient and practical means for the qualitative identification of crystalline compounds. The X-ray powder diffraction method is the only analytical method that is capable of... 

Ce2lr3Ges was found to crystallize with U2Co3Si5-type (a= 1.0189, h= 1.197, c= 0.6060 X-ray powder diffraction method) by Venturini et al. (1985b). 

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