Cell dimension and space group

From a single crystal, it is possible to measure the position and intensity of the hkl reflections accurately and from this data determine not only the unit cell dimensions and space group, but also the precise atomic positions. In most cases, this can be done with speed and accuracy, and it is one of the most powerful structural techniques available to a chemist. 

Phase angles from experimental evidence. There is another set of circumstances in which the signs of the terms can be deduced from experimental evidence. This has been done for phthalooyanine itself. It so happens that the unit cell dimensions and space-group of the parent substance and the nickel derivative are identical, and it can be assumed that the orientations of the molecules are the same in both crystals. The centre of symmetry of the cell is occupied by hydrogen... 

CA 46, 4350 (1952) [The AHC of 5-Nitro-aminotetrazole is reported as 222.6Kcal/mole] 3a) W.F. Sager D.V. Sickman, Research and Development in New Chemical High Explosives , NAVORD 483 (1952) [Addnl properties of 5-ATZ Nitrate reported are a cryst d of 1.82 g/cc and an impact sensy approaching that of Pentolite] 3b) J.H. Bryden, The Unit-Cell Dimensions and Space Groups of Some Tetrazole Compounds , ActaCryst 6, 669—70 (1953) CA 47, 10947 (1953) [Table 1, below, delineates these properties ... 

Unit Cell Dimensions and Space Groups of Some Amino-Tetrazole Compounds (Ref 3b)... 

CRYST lines, giving the unit cell dimensions and space group. 

X-ray investigations of the structure of benzene began in 1923 when Broome took the first X-ray powder photographs of the molecule. Later, Cox (1928) determined the cell dimensions and space group and showed that the molecule was at least centrosymmetric. The development of the work on the benzene structure has been reviewed by Cox (1958). A more detailed paper on the crystal structure of benzene at — 3°C (Cox et al., 1958) has established that the benzene molecule does not deviate significantly from the 6jmmm symmetry predicted by chemical theory, the maximum deviation of the carbon atoms from the mean molecular plane being 0-0013 A. 

The stmcture factors used in the determination of a model structure and the unit cell dimensions and space group are derived from diffraction patterns... 

Ellison, R. D. and Holmberg, R. W. (1960). Cell dimensions and space group of 1,l-diphenyl-2-picrylhydrazine. Acto Crystallgr, 13,446-7. [203]... 

The important preliminary data for a crystal, listed in the introduction to any crystallography article after the compound name, formula, and formula weight, are the unit cell dimensions and space group. These... 

Using known atomic positions, cell dimensions and space group symmetry, find the closest molecular pairs in the crystal, for which the distance between centers of mass is smaller than the largest molecular dimension. The number of such neighbours is usually 10-12 in organic crystals. 

MEASURING UNIT-CELL DIMENSIONS AND SPACE GROUP 6.1. Unit Cell Dimensions... 

A better technique is to have available the simulated powder patterns of all the possible tetrahedral structures so that they can be used in the same way as the JCPDS file is used to identify unknown materials. If these simulated powder patterns were available, it might not even be necessary to determine the cell dimensions and space group of an unknown molecular sieve material. For example, if the simulated powder pattern of JVS81-1 had been available, and if it matches the observed powder pattern of dehydrated VPI-5 then there would be no need to determine the correct idealized cell dimensions and symmetry. This simple comparison would have yielded the correct topology and shown that the material was an 18-ring structure. 

Using the BFDH principle and given the unit cell dimensions and space group symmetry conditions, it is possible to identify the most important morphological forms. For molecular systems this approach shows good agreement with experiment and can be used with confidence as an initial prediction of the crystal shape before refinement by further, more sophisticated energy calculations. 

Generate the crystal structure for moleeule, fiber, inorgaiue system, given a set of fractional coordinates, unit cell dimensions, and space group symmetry. All display features for the single molecules described in criterion 4 should be available for the crystal structures. In addition, a polyhedra display option should be available if inorganic structures are to be eonsidered. 

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