Crystal determinants

The Wealth of Information from Single-Crystal Determinations. The amount of information that is determined from a crystal stmcture experiment is much greater and more precise than for any other analytical tool for stmctural chemistry or stmctural molecular biology. Indeed, almost all of the stmctural information that has been deterrnined for these two fields has been derived from x-ray single crystal diffraction experiments. 

Magnetic crystals determination of magnetic point symmetry, 744... 

Weirich, T. E., Zou, X. D., Ramlau, R., Simon, A., Cascarano, G. L., Giacovazzo, C., Hovmoller, S. (2000) Structures of nanometre-size crystals determined from selected-area electron diffraction data",Hcta Cry.st. A56,29-35. 

STRUCTURES OF ZEOLITES AND MESOPOROUS CRYSTALS DETERMINED BY ELECTRON DIFFRACTION AND HIGH-RESOLUTION ELECTRON MICROSCOPY... 

Structures of zeolites and mesoporous crystals determined by electron diffraction and high-resolution electron microscopy... 

In the event, osmylation of compound 16 in pyridine, followed by the usual workup, afforded a 92% yield of an 18 1 mixture of two diols. That the major one, mp 136-139° C, has the stereochemistry implied in 20 need not be debated in light of a single crystal determination of its 7,8-bis-3,5-dinitrobenzoate derivative 21, mp 114.5-115.5° C (see Figure 5). ... 

Growth forms are the forms of a crystal determined by the structural characteristics and the effects due to environmental conditions. Assuming that a growing crystal is bounded by two F faces only, the Tracht of the crystal is determined by the... 

A key question about the transport in air or vacuum is how disordered is the DNA, particularly due to the relative absence of water. It is difficult to believe, as assumed in the calculation of Hjort and Stafstrom [71], that the DNA structure would be the same as that of a similar sequence in a crystal determined by x-rays. Note also that disorder, in being unfavorable for free carriers, is favorable for polarons. 

EtZnI (117) behaves differently because no clear solutions of this compound could be obtained in apolar solvents. Crystals of 117 suitable for an X-ray crystal determination could be obtained by crystallization of crude 117 from EtI as a solvent . The solid state structure of 117 involves the packing of four EtZnI units in an orthorhombic unit cell in such a way that each of the zinc atoms has additional bonding interactions with two iodine atoms of neighbouring EtZnI units, thus forming a coordination polymer (Figure 57) . ... 

Stop the evaporation and let the solution cool. What do you observe What is the composition of the precipitating substance Separate the crystals from the mother liquor on a funnel with a filtering bottom. Examine and draw the shape of the crystals. Determine the yield in per cent. 

A number of X-ray crystal determinations have made the principles of lanthanide cryptate structural chemistry fairly clear. In [La(N03)2(2,2,2-cryptate)][La(N03)6] (Figure 8), the La3+ ion is 12-coordinated with two bidentate nitrate ions coordinating in two of the three spaces between the cryptate chains the third space is thus too compressed to be occupied also.508 [Sm(N03)(2,2,2-cryptate)][Sm(N03)5(H20)] shows only one such space occupied511 and the structure of [Eu(C104)2,2,2-cryptate](C104)2MeCN is similar to the samarium cryptate.512,513 Intemuclear distances in these complexes are shown in Table 10. 

Fig. 102. hkO plane of reciprocal lattice of gypsum crystal, determined from iho photographs in Plate VIII. The length of each arc represent the possible error. 

Comprehensive investigations into brittleness of some crystals determined with a Vickers pyramid led Ikornikova and Khrenova (1951) to establish that crystals of mosaic structure with traces of plastic deformation are more brittle than similar crystals of homogeneous structure. Moreover it has been found (Glazov and Vigdorovich, 1969) that as the mean square displacement of the lattice structural components diminishes, in other words, as the mobility of these components diminishes with propagation of elastic waves, the ultimate effect is increased material brittleness. 

Modelling non-isothermal crystallization is the next important step in a quantitative description of reactive processing. This is particularly important, because crystallization determines the properties of the end product. Therefore, the development the spatial distribution of crystallinity, a, and temperature, T, with time throughout the volume of the reactive medium must be calculated. It is also noteworthy that crystallization and polymerization processes may occur simultaneously. This happens when polymerization proceeds at temperatures below the melting point of the newly formed polymer. A typical example of this phenomenon is anionic-activated polymerization of e-caprolactam, which takes place below the melting temperature of polycaproamide. 

The fac isomers were isolated by Schetty [31] by chromatographic separation and confirmed by Jaggi by X-ray crystal determination [32], In solution, each... 

IRE Standards on Piezoelectric Crystals determination of the elastic, piezoelectric and dielectric constants - the Electromechanical Coupling Factor, 1958, Proceedings IRE April 1958, 764-78. 

X-ray diffraction has been an extremely powerful tool for characterizing E-M complexes, and most reported here have had single-crystal determinations reported. Even more exciting results will come in the future as area detectors become more widely used. These allow for the collection of data on larger unit cells and consequently larger cluster molecules. Extended... 

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