Crystal structure single crystals

Crystal structure Single crystal and polycrystal, single crystal appearing as cubiccrystal structure, and lattice constant is 0.3559-0.3570 nm. 

Two types of diffraction measurements are typically made on cosmochemical samples. Powder diffraction, where a sample powder is mounted on the end of a fiber and placed in the X-ray beam, is most commonly used. The term powder in this usage means that the crystal lattice domains are randomly oriented. Powder diffraction is used to identify unknown materials and to determine their basic crystal structure. Single-crystal X-ray diffraction is used to solve the complete structure of crystalline materials. For more details, see Cullity (1978). 

The EPR spectrum of the blue copper protein plastocyanin (Figure 3C) has gu > g > 2.00, and thus the copper site must have a dx2 y2 ground state. First, we are interested in determining the orientation of the dx2 y2 orbital relative to the distorted tetrahedral geometry observed in the protein crystal structure. Single crystal EPR spectroscopy allowed us to obtain this orientation and located the unique (i.e., z) direction in this distorted site (29). Plastocyanin crystallizes in an orthorhombic space group with four symmetry related molecules in the unit cell. The orientation of the plastocyanin copper sites in the unit cell are shown in... 

The present work deals with soUd CT complexes of phenazines which, in the most favorable cases, include the crystal structure, single-crystal electron spin resonance (epr) data, the temperature dependence of the magnetic susceptibility or of the powder conductivity, and a CT absorption spectrum. We have not pursued complexes that could not be crystallized, nor have we investigated completely similar materials. 

Particle shape ribbon or cylinder Crystal structure single crystal... 

The highest modulus of a given substrate is obtained with a single crystal structure. Single crystal CVD-SiC whiskers (578 GPa) have a stiffen more highly ordered, structure than polycrystalline CVD-SiC fibers (190-400 GPa), and sapphire whiskers and fibers (415 GPa) are stiffer than slurry spun polycrystalline alumina fibers such as Fiber FP (380 GPa). Superimposed upon this relationship is a compositional factor. Fiber modulus and structural order generally also decrease with increasing compositional complexity, e.g., silicon carbide is intrinsically stiffer than silicon oxycarbide such as Nicalon, and slurry spun alumina fibers are stiffer than sol-gel or melt spun aluminate fibers. 

Particle shape ribbon or cylinder Crystal structure single crystal Specific surface area, m /g 2.5... 

Figure 6 Reversible adsorption of CHjCl, CHCI3, and CCI4 based on H20C[Cd(L,2)2(C104)2] [5], and their single-crystal structures. Single-crystal analysis indicates that the encapsulated chlorocarbon species are disordered in the pores, so only major disordered components are shown in the figure. The different chlorocarbon guests are shown in different colors for clarity...

The structural constraints imposed by the fused cyclic structure of the catenates and the ability to cleanly separate product mixtures greatly facilitates crystallization, and single crystal X-ray structures have been obtained for a number of ladder polysilanes.3 8 For the all-anti molecules, the non-planarity of the SI rings induces a unidirectional helical twist to the ladder structure, as is evident in Figure 63. 

Similar to Jeffrey s hypothetical structure IV, structure H is a hexagonal crystal of space group P6/mmm. However, in contrast to structure IV, structure H comprises 435663 and 51268 cavities in addition to 512 cavities. On the basis of size considerations (including the relative size of the guests, the size of the cages in I-VII, and the unit cell parameters for sH), the structure was incompatible with Jeffrey s structures. Therefore, sH is not one of Jeffrey s (1984) known or hypothetical structures. Single crystal diffraction data for structure H have been obtained by Udachin et al. (1997b, 2002) and Kirchner et al. (2004). 

The existence of two isomers of both b/s(diethyldithiocarbamato)-pyridinezinc(H), 34, and fc/5(diethyldithiocarbamato)morpholinezinc(II), 35, in the asymmetric units has been confirmed by direct structural single-crystal X-... 

Table 1. The classes of heteropolyanions of known structure. Single-crystal X-ray structure determinations (references cited) were made on the anions containing the heteroatoms in italics. For the many other heteropolyanions of unknown or uncertain structure, and for derivatives of the first two series, see text... 

X-ray structure Single-crystal X-ray diffraction analysis yields the 3-D structure of a molecule in the crystalline state. An X-ray structure is likely to be a structure in a minimum energy conformational state or close to an energy minimum. An X-ray structure therefore may or may not be the biologically relevant conformation. Inspection of the molecular packing arrangement may yield valuable information about intermolecular contacts and sites of inter-... 

X-ray analysis. In the pantheon of methods employed to elucidate structures, single-crystal Z-ray analysis reigns supreme. It deserves every chemist s respect for it unites speed, completeness, and dependability. Using a modem diffractometer for measurements and a computer for calculations, this method unequivocally establishes within a few days or weeks the composition and solid-state conformation of a small molecule. By contrast, 150 years separated the discovery of the notorious alkaloid poison strychnine and the confirmation of its complex structure by synthesis, which in 1947 culminated a half-century s chemical research. 

In the case of (a), the zero-dimensional (0-D) nanostructure is composed of nanoparticles whose fabrication requires the control of more than merely their diminutive size. For any practical applications such as electroactive components in electrodes, the processing conditions must be controlled so that the resulting nanoparticles have the following characteristics (a) identical size of aU particles (also referred to as monosized or quasi-monosized), (b) identical shape or morphology, and (c) identical or at least very similar chemical composition and crystal structure. Single crystalline nanoparticles are often referred to in the literature as nanocrystals. When the characteristic dimensions of nanoparticles are sufficiently small and quantum effects are observed, these nanoparticles are commonly... 

The restrictions on the adsorption system are minimal ordered or disordered overlayers can be examined, as can either well-structured single crystal samples or optically rough surfaces. Hence, chemisorption on evaporated films can be studied, as can the nature of metal overlayer-semiconductor interactions. In addition, coadsorbed atoms and molecules can be studied without difficulty. 

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