Title: Anomalous dispersion analyses of the Ni-atom site in an aluminophosphate test crystal including the use of tuned synchrotron radiation
Abstract:Data were collected close to the Ni K edge, using synchrotron radiation at the National Synchrotron Light Source, and using a Mo K α rotating anode, from a crystal of a nickel-containing aluminophosph...Data were collected close to the Ni K edge, using synchrotron radiation at the National Synchrotron Light Source, and using a Mo K α rotating anode, from a crystal of a nickel-containing aluminophosphate, NiAl 3 P 4 O 18 C 4 H 21 N 4 (NiAPO). These data sets, along with an existing Cu K α rotating anode data set, allowed the calculation of several f ′ difference-Fourier maps exploiting the difference in f ′ for Ni between the various wavelengths. These differences are expected to be 7.8, 4.5 and 3.3 e for Mo K α data to SR (synchrotron radiation), Cu K α to SR and Mo K α to Cu K α, respectively. The phases were calculated either excluding the Ni atom or with Al at the Ni-atom site. The f ′ difference-Fourier maps revealed peaks at the Ni-atom site, whose height and distance from the refined Ni-atom position depended on the f ' difference and the phase set used. The largest peak was located at a distance of only 0.025 Å from the refined Ni-atom site and was obtained from the f ′ difference map calculated with the coefficients | F Mo K α − F SR | , using phases calculated with Al at the Ni-atom site. In all cases, it was found that these phases gave optimal results without introducing bias into the maps. The results confirm and expand upon earlier results [Helliwell, Gallois, Kariuki, Kaučič & Helliwell (1993), Acta Cryst. B 49 , 420–428]. The techniques described are generally applicable to other systems containing anomalous scatterers in chemical crystallography.Read More
Publication Year: 1996
Publication Date: 1996-06-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 3
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