To any one that can help:
I am performing a rietveld refinement using GSAS on x-ray data of a rod material. I have thus far been able to make a good fit by simply attaining the Particle size and strain broadening. The data so far matches close to what I expect. I am using the type 2 pseudo-Voigt profile and have been trying to refine my fit with as few variables as possible. I have just recently started using the GSAS program so I have tried to use only the variables I know well. Mainly the size and strain parameters. I tried for my own curiosity to refine the Gamma variables (Gamma11,22,33,12,13,23). This has improved my refinement to a Rwp=0.14 rather than a Rwp=0.3. Since this has improved my fit I think I am using the variables correctly. So my question is:
1) What is the physical representation of these variables the gamma variable? The GSAS manual describes them as the empirical extension of the microstrain anisotropy. I know that they put weighting on the (h,k,l) coordinates to deal with line broadening but how do I know they are weighting them correctly for my hexagonal lattice?
2)From the GSAS manual (gamma=y):
yl=y11(h^2)+y22(k^2)+y33(l^2)+2*y12(hk)+2*y13(hl)+2*y23(kl)
What does this equation mean?
3) This question is on a slightly different subject: I know my material is cylindrical in shape is there a way to input this orientation into GSAS? Can someone give me a good reference in how to use either the March-Dollase Preferred Orientation or the Spherical Orientation?
Thank you to who ever can help me solve these problems.
-Darin Hoffman
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Darin Hoffman
Research Intern, NPDF
Lujan Neutron Scattering Center
Los Alamos National Laboratory
e-mail: [EMAIL PROTECTED]
PH: 505-667-8704
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