Analytical Absorption Correction (Meulenaar, Tompa & Alcock) (14/5/97)
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(see. N.W. Alcock (1990). Crystallographic Computing, p 271)

The M,T & A code has been implemented in PLATON and adapted to fit into
the direction cosine regime used with shelx-76 (compatible with
SHELXL93).

Two files are needed:

1 - instruction file: <name>.ins
2 - reflection  file: <name>.hkl   (hkl F^2 sig(F^2) + direction cosines)

The standard published testdata set is included in this directory and may be
run with:

platon abstest.ins

instruction file format:

1 - TITL <text>
2 - CELL lamda a b c alpha beta gamma
3 - FACE h k l d
       ..
4 - ABST mu

Notes:
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- d is the distance to a centre inside the crystal
- the dimensions of mu and d should be the same (i.e. cm or mm)
- Gaussian integration in place of M,T&A can be done by substituting
  the last instruction by 'ABSG mu nx ny nz', where nx, ny & nz
  are the 'gauss grid numbers in the x, y & z direction resp. 


In addition three tests (test1, test2 & stand) are provided illus-
trating the alternative use of 'absolute-psi'-values instead of
direction cosines on 'shelxl.hkl' (Adapted from the Alcock 
distribution).
