Refinement of DMC data using FULLPROF
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Fullprof recognizes the DMC data format (Ins=8).
Best fits are achieved using profile function 4 (Npr=4) in Fullprof. Besides U,V and W this peak shape requires 4 additional parameters (Shape1, X, Y, Shp1).
These parameters are instrument parameters and should not be refined. At λ = 2.45 Å we get Shape1=0, X=0.2849, Y=0.3657, Shp1=0.00787. The parameters U,V and W depend on the sample and must be refined. Possible starting values at 2.45 Å are 0.94, -0.57, 0.18. See the table below for the list of peak shape parameters at other wavelengths. It is advised to set Wdt, the cut-off of the peak profile tails, to a small number, e.g. Wdt=3.
You may as well use other profile functions, e.g. peak shape function 7 (Npr=7, see Fullprof manual). This will lead to quite similar values of the refined structural or magnetic parameters but with somewhat larger errors.
| Peak shape parameters for peak shape function 4 (Npr=4) | |||||||
|---|---|---|---|---|---|---|---|
| Wavelength | Shape1 | X | Y | Shp1 | U1) | V1) | W1) |
| 2.45 Å | 0 | 0.39068 | 0.35013 | 0.007046 | 1.03 | -0.63 | 0.21 |
| 3.80 Å | 0 | 0.33132 | 0.34197 | 0.00575 | 0.62 | -0.68 | 0.39 |
| 4.50 Å | 0 | 0.31415 | 0.32137 | 0.00521 | 0.45 | -0.43 | 0.31 |
1) starting values for refinement