Calculation Control

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Preferred Orientation Calculation Control Result Output BGMN Variables

BGMN Control File

The Rietveld calculation with BGMN is controlled by a simple text file with the file extension 'sav'. A list and extended explanation of the variables used is available.

By means of the control file for the plaster sample (plaster.sav) the necessary elements will be explained here.

First, the instrumental function (calculated with GEOMET and MAKEGEQ, see previous pages) has to be provided:

VERZERR=urdneu11.geq
Then the measuring value file is needed:
VAL[1]=kldomei5.val

This file is in the APX-63 format, a simple text format from the SEIFERT-FPM diffractometers. BGMN can process files with the extension 'rd' (Philips APD) and 'raw' (SIEMENS Diffrac-AT) as well. If you want to use other formats, you have to convert it into one of the above.

If a secondary graphite monochromator was used, an appropriate polarisation factor is (26.6 is the 2-theta angle of the graphite crystal; without monochromator use 'POL=1', which is the default):

pi=2*acos(0)
POL=sqr(cos(26.6*pi/180))
The structure files are given in this way:
STRUC[1]=quartz.str
STRUC[2]=calcite.str
STRUC[3]=gypsum.str
And the formulae for the quantitative analysis are:
GOAL[1]=quartz/(quartz+calcite+gypsum)
GOAL[2]=calcite/(quartz+calcite+gypsum)
GOAL[3]=gypsum/(quartz+calcite+gypsum)
In this file (plaster.lst) the results are written:
LIST=plaster.lst 
An output file for the peak list (plaster.par) is necessary if you want a graphical representation of the results:
OUTPUT=plaster.par      
For the easy publication of diagrams a file (plaster.dia) with measuring values, calculated, difference and background data can be written:
DIAGRAMM=plaster.dia      
Last, the global parameters for the zero point (EPS1) and sample displacement (EPS2) are included:
PARAM[1]=EPS1=0_-0.0001^0.0001
PARAM[2]=EPS2=0      
The calculation is started by the command
bgmn plaster      
and after each iteration step a line with information about the iteration number, the least squares sum and some other values is printed.

Structure Output Files

If one wants to inspect/process the resulting structure(s), three structure formats can be written: The above mentioned statements have to be included in the BGMN control file for each structure.