Reference to PSF #4 by P. Stephens is J. Appl. Cryst. (1999). 32, 281-289. Peter Y. Zavalij University Crystallographer Institute for Materials Research and Chemistry Department Binghamton University, SUNY, Vestal Pkwy, East Binghamton, NY 13902-6000, USA Tel: (607)777-4298 Fax: (607)777-4623 E-mail:[EMAIL PROTECTED] http://materials.binghamton.edu/zavalij
-----Original Message----- From: Darin Hoffman [mailto:[EMAIL PROTECTED] Sent: Monday, May 03, 2004 11:39 AM To: [EMAIL PROTECTED] 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 ################################################# Darin Hoffman Research Intern, NPDF Lujan Neutron Scattering Center Los Alamos National Laboratory e-mail: [EMAIL PROTECTED] PH: 505-667-8704 #####################################################
