Parametric or Surface Rietveld Refinement – Refining Temperature
Learning Outcomes: How to refine temperature using parametric fitting using the ZrP2O7 example in Stinton/Evans, J. Appl. Cryst. (2007) 40, 87–95. Rather than set up a file from scratch you’ll use a pre-prepared file. Key points of this example will have been discussed in the lecture.
1. Save the datafiles above to your directory.
2. Run d8_02999_35_annotate_04.inp. You should get Rwp = 31.56%. This is a three phase surface refinement using ZrP2O7 and Si and Al2O3 internal standards. 37 data sets are fitted simultaneously. This refinement has no temperature correction applied.
3. Read through the file to see how a parametric refinement of this type is set up. The file has been annotated and is discussed more in the reference above.
4. Section 6 of the file contains the temperature correction polynomial. All terms are set to 0.0 initially meaning no temperature correction. Set these terms to refine:
prm T_calibration_b 0.0 prm T_calibration_c 0.0 prm T_calibration_d 0.0
5. You should get a reduction in Rwp to 31.53%.
6. Plot out your results. If you’ve done the analysis in the order above results both with and without the temperature correction will have been written to a file called temp.res. If you use gnuplot then plotting columns 2:4 gives the delta_temperature plot, 2:7 shows cell vs set temperature, 3:7 shows cell vs refined temperature.