From what I have been told and led to believe, Chi^2 isn't the be all
and end all. This will really depend upon your counting statistics. Pay
more attention to your Rp, Rwp and what your fit actually looks like.
Also, try performing a Le Bail fit to your data and see what Chi^2 you
get. This should give you a bench mark to aim for.
Best of luck
Adrian
Mibeck, Blaise wrote:
I am re-learning GSAS to bring Rietveld to my department (for the
first time). We have an old Phillips Xpert.
I am trying to refine a quartz standard to acquire my profile and
instrument parameters for this instrument and have yet to get my Chi^2
below 500. The instrument is not in my direct control. I have caught
and asked them to correct a few problems already (dwell time too low,
aluminum sneaking into the beam, etc…) and this has helped. I would
like not to annoy them any more than I have too.
At this point I think my high Chi^2s are mainly due to low angle
asymmetric peaks that my fit is not able to copy – the asym is not
terrible but may be messing me up. I am getting better results with
peak profile functions 3 and 4, but unable to get Chi^2 below 500. My
scans go up to 70 degrees 2theta.
I would like to tell the people caring for the instrument that my
problem is on their end, but I am not confident in my own refining
skills to say this. When I work with the tutorials or standard data
from my graduate school experiment I am ok – I think I am proceeding
in a reasonable way, although I can get stuck here and there.
I would like to find out if I am doing something incorrectly or if the
problem is instrument related. I hate to bug one of you but wonder if
I could get someone to look at my work?? Is there a better forum for
asking for this kind of help?
Kindest regards to all of you,
Blaise
* * * * * * * * * * * * *
Blaise Mibeck
Research Scientist
Energy & Environmental Research Center
University of North Dakota
15 North 23rd Street, Stop 9018
Grand Forks, ND 58202-9018
Phone: (701) 777-5077
Email: [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
--
Adrian Hill
[EMAIL PROTECTED]
Centre for Science at Extreme Conditions
The University of Edinburgh
Currently based at,
The Institut Laue-Langevin
ILL4 110
BP 156
6, rue Jules Horowitz
38042 Grenoble Cedex 9
France
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.
