Single crystals data collection

Clegg, W. Mecisuring and collecting single crystal data. Notes International Summerschool on Crystallography and its Teaching. September 15-24, 1988. pp. 1-15. Tianjin Normal University Tianjin, China (1988). 

At the same time, the structural chemistry of tri- and tetravalent actinide orthophosphates is not well-known. A small number of theoretically possible compounds have been discussed [14]. The collection of information on actinide compounds may take a long period of time, on account of the experimental difficulties of work with actinides that require special conditions and equipment. Consequently, single crystal data are available for a few compounds only in most cases, the analysis was based on powder diffraction data and analogy to other structures. 

The unusual feature, plus several other structural peculiarities, led to the collection of a new set of single crystal data.62 Numerous faint reflections showed that the cell is not centered and that the true space group is Pcca. The new structure confirms the expected ionic character of this salt and contains no surprising features. 

In order to detect the diffraction data very rapidly, we have made a new photoncounting X-ray detector, MSGC, whose size is 10 cm x 10 cm. The detector can record one-shot data within 1 ms. If the crystal was rotated around the -axis on the four-circle diffractometer using the rotating anode X-ray generator and the MSGC detector, all the intensity data of a standard single crystal were collected within... 

At the various synchrotrons all these geometries have been exploited for macromolecular crystal data collection as they have also on conventional X-ray sources. Once the polychromatic synchrotron X-ray beam has been rendered monochromatic the single crystal data can be measured and processed as for a conventional X-ray source. These standard procedures will be discussed briefly before moving on to cover the synchrotron specific aspects. These latter include SR instrument... 

However it is evidently senseless to rednce single ciystal elec-trochemistiy to material science, a tool to solve some pnzzles of real materials, bnt it is easy to see that appealing to varions materials widens a field of visiom The same is with inadeqnacy of idea to put this area in frames of classical thermodynamic scheme. Following its own way, single crystal experiments collect more and more information abont behavior of 1 adlayer components, bnt keeping some traditions of data treatment wonld not be ont of place for this advanced field. The snbseqnent Sections touch briefly three points of most visible intersection. 

The Cp Ln complexes and their adducts have been studied extensively by optical spectroscopy [28]. Much of the earlier work was done by Pappalardo [29 33] but recently Amberger and his coworkers [3 -36] have started to reanalyze the old data and collect new data. Brittain et al. [37] have also reported luminescence data on (RCp ) Tb THF (R H,CH Cp =C H ). Pappalardo et al. have collected extensive line lists on a number of complexes using thin films and glasses, but the analyses have been hampered by the lack of single crystal data. In addition a number of the spectra are complicated by the presence of strong vibronic bands. 

An x-ray area detector can be used to collect the intensities of many reflections at a time. The crystal must be oriented in many different settings with respect to the incident beam but the detector needs to be positioned at only a few positions to collect all of the data. A charge coupled device (CCD) is used as the area detector on the Siemens SMART single crystal diffractometer system. The SMART detector consists of a flat 6-cm circular phosphorescent screen that converts x-ray photons to visible light photons. The screen is coupled to a tapered fiber optics bundle which is then coupled to a one inch by one inch square CCD chip. The CCD chip has 1024 x 1024 pixels each of which stores an electrical charge proportional to the number of... 

It appears that no comprehensive review was published after Perkins and Andersen s work. Nevertheless, articles devoted to particular aspects have been written. Thus collections of data were compiled by Hamelin et al.24 for single-crystal face electrodes (Cu, Ag, Au, Sn, Pb, Zn, and Bi) in 1983, by Trasatti75,26 in 1986 and 1992, by Khrushcheva and Kazarinov27 in 1986, and by Lust et al.2 in 1996 for Bi, Sb, and Cd. 

Kinetics over the Mo(lOO) Crystal Surface. We have studied the hydrodesulfurization of thiophene over the initially clean Mo(lOO) single crystal surface in the temperature range 520K - 690K and at reactant pressures of 100 Torr < P(H ) 800 Torr and 0.1 Torr P(Th) < 10 Torr. Under these conditions the reaction is catalyzed at a constant rate for a period of approximately one hour after which the rate begins to decrease with time. The rates reported here are all initial rates of reaction calculated from data collected in the period over which they remain constant. 

There are many variants of this system which can be envisaged as means by which the current possibilities for automation in data collection can be applied for specific purposes. There are considerable dangers in this approach in that it may be all too easy to build in restrictions which predetermine the results. These dangers, however, are not likely to be worse than those normally encountered in electron microscopy or single crystal diffraction where the one particularly "good-looking picture is taken as being "typical" of a sample. 

Electrochemical nuclear magnetic resonance (NMR) is a relatively new technique that has recently been reviewed (Babu et al., 2003). NMR has low sensitivity, and a typical high-held NMR instrument needs 10 to 10 NMR active atoms (e.g., spins), to collect good data in a reasonable time period. Since 1 cm of a single-crystal metal contains about 10 atoms, at least 1 m of surface area is needed to meet the NMR sensitivity requirement. This can be met by working with carbon-supported platinum... 

X-ray single crystal analysis Data collection. Siemens SMART IK CCD. Diffractometer. Data collection by SMART (Siemens, 1995) cell refinement SMART data reduction SAINT (Siemens, 1995) program(s) used to solve structure SHELXS97 (Sheldrick, 1997) program(s) used to refine structure SHELXL97 (Sheldrick, 1997) molecular graphics XP in SHELXTL (Sheldrick,... 

Figure 4 Diagrammatic representation of single-crystal x-ray diffraction and data collection.

Nitromalonamide was synthesized according to Hantzsch [10]. Single crystals were grown by evaporation from a methoxy-ethanol solution. The crystal used for data collection was glued to a few carbon fibres stuck on a copper wire for better thermal... 

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