Jon: The way to do it is to in fact use two phases, and constrain all the structural parameters to be the same. I have used this approach successfully on a similar problem. Jim Kaduk > ---------- > From: Jon Wright[SMTP:[EMAIL PROTECTED]] > Reply To: RIETVELD_L Distribution List > Sent: Tuesday, March 21, 2000 1:54 PM > To: RIETVELD_L Distribution List > Subject: Fitting lorentzian tails in GSAS > > Hi all, > > I've got some high resolution data from a synchrotron with quite a lot of > sample broadening. A quick go with a curve fitting program has shown that > the fitting a pseudo-voigt peakshape leads to a negative eta parameter. So > it is more that 100% "lorentzian" in character. I can get quite nice fits > to individual peaks with a sum of two lorentzians, or with the strange > pseudo-voigt. To refine the data I want to give a peakshape like this to a > Reitveld refinement program. > > Can this be done with GSAS without using more than one crystallographic > phase? As far as I can tell the answer is no - can anyone tell me > otherwise or lend any handy hints? I'd like to be doing a combined fit of > this data with some high resolution TOF neutron data at some point in the > future, which seems to rule out many other programs. > > Pointers to source code for a suitable peakshape (with an low angle > asymmetry correction) would be also be appreciated. > > Thanks in advance, > > Jon Wright > > ========================================================================== > == > Dept. of Chemistry, Lensfield Road, Cambridge, CB2 1EW > Phone-Office 01223 (3)36396; Lab 01223 (3)36305; Home 01223 462024 >
