RE: Anisotropic line broadening in cubic material

2004-08-23 Thread pstephens
Jens, Your effect might be more related to strain than size broadening. You would have to check widths at various diffraction orders in a given direction (i.e., 111, 222, 333, etc., vs 200, 400, 600, etc. for an fcc material). If the widths increase roughly in proportion to diffraction orde

Optics puzzle

2004-08-23 Thread Whitfield, Pamela
Hiya all I have a bit of a brainache for a Monday morning.   We ran a couple of samples on a Scintag Bragg-Brentano diffractometer and found some weak reflections that would correspond to a doubled c-axis supercell.  I was a bit wary, so I ran it on our twin mirror D8 this weekend - and fou

RE: Rietveld refinement and PDF refinement ?

2004-08-23 Thread Radaelli, PG (Paolo)
> do you really have the > resolution even on > HRPD to see the diffuse scattering between Bragg peaks at > high Q ? No we don't, but this is not the main point (by the way, we don't use HRPD for PDF, it doesn't go to sufficiently short wavelengths). The main reason to go to high Q is to avoid

Modesty

2004-08-23 Thread Armel Le Bail
And he is modest as well :-) I have to be modest. According to the CNRS, I am a second-class researcher... Armel

Re: step scan increments

2004-08-23 Thread Armel Le Bail
Can anyone indicate me how must I choice the 2theta step increment and the total experiment time of step scan DRX pattern for having a good rietveld refinment result. The step increment choice depends on the instrument resolution. Determine what is your sample minimal full width at half maximum,

Re: Rietveld refinement and PDF refinement ?

2004-08-23 Thread Jon Wright
Bob, This exactly what is needed when the sample is a mixture of amorphous and crystalline components. But what happens when the material is a single crystalline phase with some coherent defects? Don't the defect <-> average structure correlations start to dominate, and separating components is