CCP14
Methods, Problems and Solutions
GSAS (General Structure Analysis System) Rietveld powder diffraction and Single Crystal software
GSAS - and variable step/almost constant step data
The CCP14 Homepage is at http://www.ccp14.ac.uk
[The reference to use for GSAS in any resulting publications is:
A.C. Larson and R.B. Von Dreele, "General Structure Analysis System
(GSAS)", Los Alamos National Laboratory Report LAUR 86-748 (1994).]
>Date: Mon, 10 May 1999 13:13:30 -0600
>To: L.M.D.Cranswick@dl.ac.uk (L. Cranswick)
>From: vondreele@popler.lansce.lanl.gov (Bob Von Dreele)
>Subject: Re: Variable Step data and GSAS Query
Assuming that the data is "constant" step data where the diffractometer
can't make precisely the same step each time, this data can be read in
"as-is" to GSAS. You need to use the "ALT" input format which reads in
position, intensity & esd for each step. The position value is
32*centidegrees. This may seem odd but it was developed to read in the
weird TOF steps generated by the ISIS data acquisition systems. On the
"BANK" card use "CONST" for the step algorithm and enter the zero and step
size in 32*centidegrees. The step should be the mean step size.
Bob