On 3 May 2005 at 10:51, Jon Wright wrote: > > > Silly question and I think I am missing the point - but how did you fix > the vertical divergence contribution? I thought LaB6 from NIST had a > larger crystallite size than either of your values, suggesting something > has gone wrong in both cases. If the program thinks you have a lot of > sample broadening, when in reality LaB6 was chosen for having very > little, it is probably missing a contribution of the instrument. You > appear to have forced that instrumental thing be Lorentzian by refining > only CS_L. Maybe just refine CS_L and CS_G together? This is unlikely to > solve your problem but remember powder diffraction is only really good > for measuring crystallite size when there is an appreciable size > broadening compared to a line shape standard like LaB6! > > And no one has mentioned "tube tails" yet ;-) > yes, I think that I am missing an instrumental thing and yes, I did not refine the gaussian contribution. If I do that, I get 395+217 for the 1/4 case and 419+413 for the 1/32 case. What should it be for LaB6? And no, my aim is not to get the crystallite size for LaB6, but I note that if I remove the crystallite size contribution that my the generated peak is much too small, so indeed, there is something lacking. Last point, what do you mean by vertical divergence? The Topas manual defines the 'axial divergence' which can be limited by soller slits, and the 'horizontal divergence in the equitorial plane', which is, I think, the divergence perpendicular to the axial divergence. Whether you call it horizontal or vertical depends on whether you have a horizontal or vertical goniometer .
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