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Item _refine.ls_extinction_method

Description

              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.