Analysing Friedel averages and differences.
Acta Crystallogr A
; 68(Pt 6): 736-49, 2012 Nov.
Article
in En
| MEDLINE
| ID: mdl-23075616
ABSTRACT
Various practical applications of the average (A) and difference (D) of Friedel opposites are described. Techniques based on the resonant-scattering contribution to Friedel differences are applied to see whether a crystal is centrosymmetric or not, and to determine the point group of the crystal. For the validation of a structural study, plots of A(obs) against A(model), and D(obs) against D(model) are used extensively. Moreover, it is useful to display both plots on the same graph. Intensity measurements on a crystal of NaClO(3) were made at three different speeds, with two different radiations and two different diffractometers, and treated with two different software packages and four different absorption corrections. The evaluation of these numerous data sets reveals underlying deficiencies. For comparison, plots of A(obs) against A(model), and D(obs) against D(model) are presented for two centrosymmetric crystals.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
Acta Crystallogr A
Year:
2012
Document type:
Article
Affiliation country:
United kingdom