Note that the radius datum has now been accepted (green) and the next data item ready to go
(mu 1.5).
The next window (alter entering the mu value) looks like
Fig. 4
.
The actual calculations are started by clicking on 'next-step'.
A summary of the results of the calculations is shown in
Fig.5
The transmission range without (around 1.0) and including spherical correction are given in
the lower left corner.
The calculations are terminated by clicking on 'END'.
The corrected data are on shelx.hkp and a more detailed listing on shelx.hkl.
1.3.5.2 - ABSP - PSI-Scan Based Correction for Absorption
This correction method for absorption is meant for serial detector CAD4 data only !
The related Keyboard Instruction:
ABSP (NOCHECK)(LIST)
Sub-Menu #0 – (
Section 1.4.16) – Options
PLATON/ABSP for psi-scan based absorption correction requires two files
1.
shelxl.ins : An instruction file
2.
shelxl.hkl : A reflection file (SHELX HKLF 4 + Direction Cosines)
The content of the instruction file (shelxl.ins) should look like
TITL S588A
CELL 0.71073 11.1364 12.0577 15.3782 90 90 90
ABSP
Notes:
- The shelxl.hkl file should contain two sections, separated by a blank line.
- The psi-scan data should go in the second section.
- Such a file is produced for CAD4 data using the (local) data reduction program
HELENA which is included in the PLATON source (see Appendix VII).
- Each psi-scan (10 degree steps) should consist of 36 measurements. (or 37 with
endpoint = begin + 360 degrees).
- Include the instructions 'MENU OFF' and 'SET DISPLAY OFF' before 'ABSP' for a
non-interactive graphics run.
-Theta dependence of the absorption may be modelled with an additional spherical
correction by supplying a
MuR value on the ABSP instruction line or from the menu.
The calculations may be invoked through:
platon shelxl.ins
The corrected data are written to:
shelxl.hkp
See for
EXAMPLE DATA
s588a.ins, s588a.hkl & s588a.lis
1.3.5.3 - ABST - Analytical Absorption Correction
Analytical absorption correction following the de Meulenaer & Tompa (1965) algorithm
(see. Alcock (1970). The de Meulenaer,Tompa & Alcock code for numerical absorption
correction 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:
ABST mu (NOCHECK)(LIST)
Where
mu linear absorption coefficient (mm or cm depending on FACE)
NOCHECK Optional: for accepting direction cosines without checking. This option should
be used with care.
LIST Optional listing of reflections with corrections.
Two files are needed for the calculations:
1.
name.ins : instruction file:
2.
name.hkl : reflection file: (hkl F^2 sig(F^2) + direction cosines)