Item _refine.ls_extinction_method

Description

              A description of the extinction correction method applied with
               the data item _refine.ls_extinction_coef. 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,
                    129-153.
                    Zachariasen, W. H. (1967). Acta Cryst. 23, 558- 564.
                    Larson, A. C. (1967). Acta Cryst. 23, 664-665.

Category

Item Examples

Example 1:

B-C type 2 Gaussian isotropic

Mandatory Code

Data Type Code

Default Value

Alias Names