Negative Equivalent Isotrpic Calculated Values Problem..

All, I am refining some TOF powder neutron diffraction data (GEM Xpress) using GSAS, when I refine with isotropic displacement parameters I get reasonable and consistent values. However, when I refine using anisotropic displacement parameters the equivalent isotropic calculated from these are almo

Rietveld Package...

Dear All, Does anyone have any experience or comments about the Accelrys software REFLEX for Phase ID and Rietveld refinement? I currently use both GSAS and TOPAS for such tasks but I am having a meeting with them soon, to see what they can offer, and would appreciate any comments. Many thanks,

Rietveld Package.

Dear All, Does anyone have any experience or comments about the Accelrys software REFLEX for Phase ID and Rietveld refinement? I currently use both GSAS and TOPAS for such tasks but I am having a meeting with them soon, to see what they can offer, and would appreciate any comments. Many thanks,

Question on file formats

I have a question for the list... I have some ToF data from GEM ISIS as both a .gss and a .asc file. I have managed to import and refine this using GSAS but am having some difficulties importing into TOPAS. Does anyone have some advice please on maybe file exchange or getting this file into the

Question on QPA - Amorphous/crystalline mix

I have a question for the list as I know there are a number of people working on QPA. Ok the question is as follows:- We have a mixture of a number of crystalline phases (A and B) and an amorphous (glassy) phase. We can do Rietveld refinement on this and get weight percentage (wt.%) values for the