Difference between revisions of "Centric and acentric distribution"
From Online Dictionary of Crystallography
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==Definition== | ==Definition== | ||
| − | Centric or acentric distribution usually refer to the X-ray diffracted intensity distribution. It is in general possible to distinguish between a centrosymmetric or a non-centrosymmetric space group by considering their intensity distribution. The figure below represents the | + | Centric or acentric distribution usually refer to the X-ray diffracted intensity distribution. It is in general possible to distinguish between a centrosymmetric or a non-centrosymmetric space group by considering their intensity distribution. The figure below represents the theoretical cumulative intensity curves for the acentric, centric and hypercentric-distributions as fraction of the means intensity |
[[File:Cumu.jpg|center]] | [[File:Cumu.jpg|center]] | ||
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| + | In practice, it is not always possible to clearly distinguish between a centric and an acentric distribution. This is specifically the case for inorganic material with highly symmetric structures. For organic molecules and in the absence of twinning, the cumulative plot are very often close to the theoretical values. | ||
== See also == | == See also == | ||
| − | Wilson, A. J. C. (1949) | + | |
| + | [https://journals.iucr.org/q/issues/1949/05/00/a00174/a00174.pdf Wilson, A. J. C. (1949) The probability distribution of X-ray intensities] | ||
Latest revision as of 07:58, 23 February 2026
Definition
Centric or acentric distribution usually refer to the X-ray diffracted intensity distribution. It is in general possible to distinguish between a centrosymmetric or a non-centrosymmetric space group by considering their intensity distribution. The figure below represents the theoretical cumulative intensity curves for the acentric, centric and hypercentric-distributions as fraction of the means intensity
In practice, it is not always possible to clearly distinguish between a centric and an acentric distribution. This is specifically the case for inorganic material with highly symmetric structures. For organic molecules and in the absence of twinning, the cumulative plot are very often close to the theoretical values.
See also
Wilson, A. J. C. (1949) The probability distribution of X-ray intensities