[sdpd] Re: nanocrystallites+Instr.Resolution

[Jon Wright <jpw22...@cus.cam.ac.uk>]

On Mon, 24 Jan 2000, Guilhem Dezanneau wrote:

> My question is:
> Am i doing well ? or are there programs that allow to fit peaks with  
> voigt function, with Ka1 and Ka2, and a knwon ratio between the two
> wavelengths ?

I think there is a Voigt function buried in the CCSL profile refinement
programs, which also includes an axial divergence asymetry correction 
(routine pfcn03). As it's only available as source code this may not be
terribly useful for you. It sounds like what you want to do was all there
with the SAPS (Structure And Peak Shape) stuff in CCSL, you could refine
the gaussian and lorentzian components in a voigt for each bragg peak, but
I don't think the Ka1 and Ka2 were really working. This was all done for
HRPD at ISIS and there are working executables kicking around for that TOF
neutron instrument at least. 

So in theory the source is there, and if you are prepared to do quite a
lot of work it could be useful. But if you already have a nice fit to your
peakshape you probably aren't going to gain very much by using a full
voigt instead of a PV or anything else. 

Hope this helps,

Jon


PS: There is also J.Appl.Cryst paper by Bill David from some years back
where a voigt function is parameterised as a psuedo-voigt - which may or
may not be of use to you?

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