ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Film-recorded neutron intensities from modified Laue measurements (a convergent-beam technique) were evaluated quantitatively and a crystal structure was refined. About 4000 reflexions were collected on 60 films in altogether 30 hours exposure of a 0.3 mm3 crystal of L-histidine. HCl. H2O, space group P212121 with a = 15.36, b = 8.92 and c = 6.88 Å. The corrections necessary for this technique are described. The structure factors were derived from the optical densities scanned by an automatic microdensitometer and processed by computer programs. Refinement on 741 symmetry-independent reflexions yielded R(F2) = 0.121. The parameters obtained are compared with those from conventional four-circle work. The mean differences in the positional parameters are 0.009 Å for C, O and Cl and 0.022 Å for H. For the anisotropic temperature factors Uij differences of 0.0054 and 0.0105 Å2 for heavy atoms and hydrogens respectively were observed between the results of the two techniques. A hydrogen atom misplaced in earlier X-ray work was located from film data collected in only 15 hours.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739477001612
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