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urdneu11.sav
) was written for the calculation of the
instrumental function (all values in mm):
% instrumental function (1st step) VERZERR=urdneu11.ger % interpolated instrumental function (2nd step) GEQ=urdneu11.geq % Device geometry (REFLEXION/TRANSMISSION/CAPILLARY) GEOMETRY=REFLEXION % Measuring circle radius R=200 % Focus dimensions of the X-ray tube FocusH=12 FocusW=0.04 % Dimensions of the divergence slit HSlitW=0.5 % Distance of divergence slit to goniometer axis HSlitR=R-72 % Dimensions of the axial divergence slit (if present) VSlitH=15 VSlitR=R-90 % Aperture of the primary collimator (if present) PColl=0.5/14 % Sample diameter SamplD=25 % Aperture of the secondary collimator (if present) SColl=0.5/14 % Dimensions of the receiving slit DetH=15 DetW=0.25 % Distance of a secondary monochromator from the sample MonR=R+50 % 2-theta angles for the raytracing calculation (1st step) zweiTheta[1]=6 zweiTheta[2]=10 zweiTheta[3]=16 zweiTheta[4]=24 zweiTheta[5]=34 zweiTheta[6]=48 zweiTheta[7]=60 zweiTheta[8]=90 zweiTheta[9]=120 zweiTheta[10]=150 % Intensity correction for small samples GSUM=Y % Angular raster for the interpolation (with makegeq) WMIN=6 WMAX=150 pi=2*acos(0) WSTEP=3*sin(pi*zweiTheta/180)
A more extended explanation of the variables used is available.
The calculation is carried out in two steps. First, a raytracing algorithm
models the distorted profiles at discrete 2-theta-angles
(zweiTheta[..]
).
The command is:
geomet urdneu11
A raytracing algorithm needs to model millions of events. Don't wonder if the calculation is time-intensive. After the raytracing calculation an interpolation is necessary to construct a file for the Rietveld calculation with BGMN:
makegeq urdneu11Now the instrumental function is ready to use. You can display its shape at each 2-theta position with the command:
showger urdneu11 2-theta-value
As a brandnew option, you may include the switch
Extension=Yinto the file
gertest.cfg
. In this case, the extension of
the calculated profile to squared Lorentzians is plotted on the screen,
too. (New feature of version 2.2.8).
In the figure the shape of the instrumental function for 2-theta=20 degree is shown.
Please note the distortion and the shift of the maximum to lower angles.These effects are later automatically considered in the Rietveld calculation. You can see some more
and explanations to this problem.