When performing high temperature/high pressure and/or phase transition experiments, it can be important to determine the unit cell results as quickly as possible so this information can be used to plan the next experiment. With Rietveld software using structureless Le Bail fitting, this becomes quite possible even on low quality patterns with impurity peaks due to the whole pattern Le Bail fitting refinement being limited to HKL lines defined by the cell and spacegroup. This can result in a very high quality unit cell refinement with overlapping impurity reflections becoming obvious. A trick here (that should work with other software such as Fullprof, Powder Cell etc) with LHPM-Rietica is to copy over the optimised HKL file to the next file in the series. This assumes you have optimised your first (and checked out the middle and end pattern of the series). For information on setting up the first file, refer to Setting up Rietica for doing Le Bail whole profile unit cell refinement In the following example, initial optimisation found that for this data (Cubic I A 3 D with a=b=c=11.82):
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Optimising the first pattern in the seriesThis has probably been done already but optimise the first dataset in your file sequence by slowing releasing parameters; and get the best fit possible. (don't forget to press the Finish Icon so that the newly refined parameters are updated). For information on setting up the first file, refer to Setting up Rietica for doing Le Bail whole profile unit cell refinement
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Applying the Previous HKL and Input files to the next dataset of the seriesNow using the Windows Explorer (or your favourite file manager) copy over the filename.HKL file and rename it to the next filename in the sequence (i.e., in this case from 0001.HKL to 0002.HKL) where Rietica will use this as your starting intensities.Now in LHPM-Rietica use File, Save As to save your input file to the new INP file (i.e., in this case from 0001.INP to 0002.INP). There should be no need to turn off parameters as everything should be stable enough to refine to convergence.
Another quick way of copying Daresbury 16.4 style files is to create a small bat file called c.bat with the following: copy 000%1.inp 000%2.inp copy 000%1.hkl 000%2.hklTo copy over the files, via a DOS box, type: c 01 02 (then refine using Rietica on the new set of files) c 02 03 (then refine using Rietica on the new set of files) etc, etc
Now refine. (you can use F10 as a speed key). Don't forget to press the Finish Icon so that the newly refined parameters are updated.
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Taking care that the refinement is looking sensible, repeat the above ad-infinitum until
you have crunched your data.
Applying HKL and input files from dataset 2 to dataset 3
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Applying HKL and input files from dataset 3 to dataset 4 |
Applying HKL and input files from dataset 4 to dataset 5 |
Applying HKL and input files from dataset 5 to dataset 6
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