Index

Macromolecular dictionary (mmCIF) version 2.0.09

_refine.ls_extinction_method

Definition:

   A description of the extinction-correction method applied.
   This description should
   include information about the correction method, either
   'Becker-Coppens' or 'Zachariasen'.  The latter is sometimes
   referred to as the 'Larson' method even though it employs
   Zachariasen's formula.

   The Becker-Coppens procedure is referred to as 'type 1' when
   correcting secondary extinction dominated by the mosaic spread;
   as 'type 2' when secondary extinction is dominated by particle
   size and includes a primary extinction component; and as 'mixed'
   when there is a mixture of types 1 and 2.

   For the Becker-Coppens method, it is also necessary to set the
   mosaic distribution as either 'Gaussian' or 'Lorentzian' and the
   nature of the extinction as 'isotropic' or 'anisotropic'. Note
   that if either the 'mixed' or 'anisotropic' corrections are
   applied, the multiple coefficients cannot be contained in
   *_extinction_coef and must be listed in _refine.details.

   Ref: Becker, P. J. & Coppens, P. (1974). Acta Cryst. A30,
        129-147, 148-153.
        Zachariasen, W. H. (1967). Acta Cryst. 23, 558- 564.
        Larson, A. C. (1967). Acta Cryst. 23, 664-665.

Type: text

Mandatory item: no

Category: refine