The performance of the Siemens SMART CCD (charge-coupled device) area detector has been tested to assess its suitability for accurate electron-density (ED) determination. 92043 diffraction intensities (14701 unique reflections, 65 h experiment) have been collected on a reference crystal of methyl 2-[(4-butyl-2-methyl-6-oxo-5-{4-[2-(1H-tetrazol-5-yl)phenyl]benzyl}-1,2- dihydropyrimidin-1-yl)methyl]-3-thiophenecarboxylate (C-30- H30N6O3S) at T = 120 K and compared with those (51485, 14699 unique, 600 h) obtained from a previous collection at T = 18 K on the same crystal using a diffractometer equipped with a conventional detector. Results from spherical and multipolar refinements (agreement factors, standard uncertainties of refined variables and geometries after correction for thermal motion) have also been compared. The lambda/2 contamination, which affects area detectors but not well tuned conventional detectors, has been carefully investigated and proved to be a negligible source of errors (which can anyway be easily corrected). The encouraging results of this test prove that area detectors are also well suited for charge-density studies, offering a cheap and fast data-collection mode, without loss of accuracy, which can be exploited for ED studies on large systems.

A test of the suitability of CCD area detectors for accurate electron-density studies / P. Macchi, D.M. Proserpio, A. Sironi, R. Soave, R. Destro. - In: JOURNAL OF APPLIED CRYSTALLOGRAPHY. - ISSN 0021-8898. - 31:4(1998), pp. 583-588.

A test of the suitability of CCD area detectors for accurate electron-density studies

P. Macchi
Primo
;
D.M. Proserpio
Secondo
;
A. Sironi;R. Soave
Penultimo
;
R. Destro
Ultimo
1998

Abstract

The performance of the Siemens SMART CCD (charge-coupled device) area detector has been tested to assess its suitability for accurate electron-density (ED) determination. 92043 diffraction intensities (14701 unique reflections, 65 h experiment) have been collected on a reference crystal of methyl 2-[(4-butyl-2-methyl-6-oxo-5-{4-[2-(1H-tetrazol-5-yl)phenyl]benzyl}-1,2- dihydropyrimidin-1-yl)methyl]-3-thiophenecarboxylate (C-30- H30N6O3S) at T = 120 K and compared with those (51485, 14699 unique, 600 h) obtained from a previous collection at T = 18 K on the same crystal using a diffractometer equipped with a conventional detector. Results from spherical and multipolar refinements (agreement factors, standard uncertainties of refined variables and geometries after correction for thermal motion) have also been compared. The lambda/2 contamination, which affects area detectors but not well tuned conventional detectors, has been carefully investigated and proved to be a negligible source of errors (which can anyway be easily corrected). The encouraging results of this test prove that area detectors are also well suited for charge-density studies, offering a cheap and fast data-collection mode, without loss of accuracy, which can be exploited for ED studies on large systems.
Settore CHIM/03 - Chimica Generale e Inorganica
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/178859
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