Topas FP Refinements

Inclusion of fundamental parameters will improve the description of the diffractometer geometry, and enable the calculation of the apparent particle size and strain.

I11 Instrumental parameters for refinements using TOPAS

Primary radius

Source to sample (Rp) = 48000 mm

Secondary radius

Sample to multi-analysing crystals (Rs), MAC = 430 mm

Detector Slits Width

Each analysing crystal acts as a very fine slit determined by the narrow rocking curve of Si(111). At 15 keV, the nominal operating energy, the acceptance angle (rocking curve) is 1 mdeg. With Rs=430 mm, the effective slits size is 0.01 mm. In our technical paper (Thompson et al, 2009), an acceptance angle of ~2 mdeg was measured, therefore an effective slit size of 0.015 mm can be used.

Slit_width(0.015)

Sample Topas input files are provided below:

FP Pawley fit of LaB6

FP Lebail fit of LaB6

FP Rietveld refinement of LaB6

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