Software FAQs

Analysing data collected on beamline I11 requires consideration of the the type of information you are hoping to extract from your experiments before your beamtime. You should clearly set out what you hope to achieve from your data collection and analysis before embarking on your experiment or refinement. There is a large difference in the processes required for phase identification compared with Rietveld refinement of your structures.

Please note that at I11 we have a range of data analysis software available, but Topas is mainly supported.  We expect that when you arrive you will be able to analysis your own data and extract the relevant information. We are happy to help you with difficult data, but there are no guarantees.

We have received many enquiries from previous users about refinement procedures, and so we have provided below answers to some of the most frequently asked questions in analysis of synchrotron data.

• Before beginning any refinement, you will need to ask your local contact for the wavelength and zero point, which is acquired from refinement of the pattern from the most recent data collection of Si NIST 640c standard.

Topas

- Change the wavelength and zero point to that provided to you by your local contact

- When you set up your refinement, it is vital to remember that the orientation of the beamline is not the same as your home machine, and so the LP factor should be set to 90 rather than 0. The parallel nature of the beam should be accounted for by changing 'lh' to 0.0001.

- Axial divergence - A good approximation is the simple axial model (Cheary and Coehlo, 1998). It is advisable to initially fix the starting parameter at 5° as shown below.

 Simple_Axial_Model(!axial, 5)

- If you are interested in calculating apparent particle size and strain, please refer to Topas Fundamental Parameter Refinements

Sample .inp files are provided below for reference

I11 Pawley fit of LaB6

I11 Rietveld refinement of LaB6

I11 Pawley fit of Silicon NIST 640c

GSAS

 - Change the wavelength and zero point in EXPGUI/GSAS to that provided to you by your local contact

 - A GSAS instrumental parameter file for silicon (NIST 640c standard) is provided below as a starting point for refinement. 

Further information about the beamline is available from the following article:

S. P. Thompson, J. E. Parker, J. Potter, T. P. Hill, A. Birt, T. M. Cobb, F. Yuan, and C. C. Tang, Rev. Sci. Instrum. 2009, 80, 075107-1.

Beamline I11 at Diamond: A new instrument for high resolution powder diffraction