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Tutorials and Examples

Powder Cell for Windows, Structure Visualisation/Manipulation, Powder Pattern Calculation and Profile Fitting by Werner Kraus and Gert Nolze

Performing Le Bail structureless whole pattern fitting using Powder Cell

The CCP14 Homepage is at http://www.ccp14.ac.uk
[Tutorials page] | [PowderCell Tutorial Index] | [Le Bail Method Homepage]

The following run-through is for Powder Cell 2.3 You may find for more complicated data involving nasty backgrounds and peak anisotropy, other programs such as LHPM-Rietica, Fullprof, GSAS, etc should be used to handle this. Powder Cell provides a very easy interface to perform simple Le Bail fitting.

We will be using Cubic Y2O3 as the example to be profiled using the following starting information 

Spacegroup = I A 3 - (206)
CELL is 10.5981 10.5981 10.5981 90 90 90

For strutureless Le Bail fitting, Powder Cell 2.3 may complain there are no atoms but just ignore this (or you can give it a "dummy" atom to stop it complaining). You can also load any struture and just change the cell and spacegroup. For Le Bail, Powder Cell will ignore the atomic information.

Open up your powder diffraction data using Diffraction, Load Powder Pattern.

In this case, we will enter a new structure from scratch by selecting File, New.

Enter the Spacegroup and Cell and Press OK. Powder Cell will complain there are no atoms but just ignore this. 

Spacegroup = I A 3 - (206)
CELL is 10.5981 10.5981 10.5981 90 90 90
To start the Le Bailing Fitting, enter Special, Decomposition and Refinement

Now select GO and the Le Bail fitting should start and converge. If it does not, enter Refinement, Parameters and deselect some relevant parameters which may be dependent on the type of pattern you are trying to fit.

Done. With the Green different plot below the powder pattern. Display options can be enabled and disabled by selecting the right mouse button and the required option. An HKL file will be present in the same directory as the powder data and there is also the option of reading in Shelx files to optimise them to the powder data.

[Tutorials page] | [PowderCell Tutorial Index] | [Le Bail Method Homepage]
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