with SHELXL HKLF 4 format (3I4, 2F8.2,I4,6F8.5).
PLATON/ABST instruction file format:
TITL text
CELL lambda a b c alpha beta gamma
FACE h k l d
...(etc)...
ABST mu
Notes:
- d is the distance to a choosen reference centre inside the crystal
- the dimensions of mu and d should be the same (i.e.
mm or cm and their
corresponding reciprocals)
- Gaussian integration instead 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.
PLATON/ABST may be run for
name.ins through:
platon name.ins
The corrected data are written to (SHELX HKLF 4 style):
name.hkp
The standard published testdata (Alcock, N.W. (1974). Acta Cryst, A40, 332-335.) set
'abstest' is included below and may be run with:
platon abstest.ins
Three additional tests (test1, test2 & stand) are provided on the
ftp-server
illustrating the
alternative use of 'absolute-psi'-values (Flack et al.) instead of direction cosines on
'shelxl.hkl' (Adapted from the Alcock distribution):
Absorption Correction Test Data and Results
Contents of abstest.ins:
TITL ABSTEST
CELL 1.5418 10.0006 11.0002 12.0012 95.81 101.31 106.8
FACE 1 0 0 1
FACE 0 1 1 1.5
FACE 0 -2 1 0.5
FACE -3 0 1 0.3
FACE 1 1 -4 1.3
ABST 1.0
Contents of abstest.hkl
0 1 1 734 2 1-0.76194 0.84042-0.24264 0.41352 0.44558-0.28769
0 1 1 734 2 1-0.87952 0.95800-0.01798 0.18886 0.19452-0.03663
0 0 1 454 2 1-0.83199 0.86344-0.69424 0.71659 0.06645 0.06645
0 0 -1 454 2 1 0.83199-0.86344 0.69424-0.71659-0.06645-0.06645
1 2 3 2255 2 1-0.53890 0.89307 0.01820 0.39840 0.68323-0.19531
1 2 -3 888 2 1 0.28445-0.11900 0.92766-0.64519 0.51498-0.82452
1 -2 3 1355 2 1-0.53152 0.69757-0.97176 0.79426-0.20838 0.59637
1 -2 3 1355 2 1-0.74569 0.91174-0.82812 0.65061-0.01234 0.40032
0 0 -1 1336.56 5.89 0.33968 8.51033344209
1 2 3 7047.89 6.25 0.31995 8.51033344209
1 2 -3 5286.08 11.91 0.16799 8.51033344209
1 -2 3 5287.38 7.80 0.25627 8.51033344209
1 -2 3 4360.63 6.44 0.31073 8.51033344209
1 -2 -3 5513.00 5.96 0.33575 8.51033344209
-1 2 3 5513.00 5.96 0.33575 8.51033344209
-1 2 -3 5285.33 7.52 0.26583 8.51033344209
-1 -2 3 5283.90 11.28 0.17733 8.51033344209
-1 -2 -3 7045.97 6.30 0.31749 8.51033344209
:: Array Size Needed = 340
:: 13 Reflections Processed
:: MIN Transmission = 0.16799 for the 1, 2, -3
:: MAX Transmission = 0.33968 for the 0, 0, 1
:: MEAN Transmission = 0.29318
:: Average Time per Reflection = 0.0013 Seconds
1.3.5.4 - ABSG – Correction for Absorption with Gaussian Integration
Absorption correction based on face indexing and integration on a Gaussian grid. A
modified version of the Coppens code (see Crystallographic Computing, 1970) has been
implemented in PLATON and adapted to fit into the direction cosine regime introduced with
SHELX-76 (compatible with SHELXL97).
Sub-Menu #0 – (
Section 1.4.16) – Options
The related keyboard instruction:
ABSG mu (nx ny nz) (NOCHECK)(LIST)
Two files are needed:
1.
name.ins : instruction file
2.
name.hkl : reflection file (h,k,l,F^2,sig(F^2) + direction cosines)
with SHELXL HKLF 4 format (3I4, 2F8.2,I4,6F8.5).
PLATON/ABSG instruction file format:
TITL text
CELL lamda a b c alpha beta gamma
FACE h k l d
...(etc)...
ABSG mu (nx ny nz)
Notes:
-
d on the FACE record is the distance to a chosen reference centre inside the crystal
- the dimensions of mu and d should be the same (i.e.
mm or
cm and their
corresponding reciprocals)
-
nx,
ny &
nz are the 'Gauss grid numbers in the x, y & z direction respectively.
The Gauss numbers can be omitted or set to even numbers (e.g. 8).
High values (e.g. 32) should give accurate values similar to those obtained with
ABST.
However, computing time increases rapidly with increasing Gauss number values.
PLATON/ABSG may be run for
name.ins through:
platon name.ins
The corrected data are written to (SHELX HKLF 4 style):
name.hkp