Centric and acentric distribution

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