I am trying to refine XRD data with Rhombohedral phase of space group R3m with a=b=c and angles = 89.8 degree
In High Score Plus, it is giving error like "Invalid space group setting for R3m"
Can anyone suggest what it means and how to resolve it?
There are two possible settings for the rhombohedral space groups:
1. a=b=c and α=β=γ (rhombohedral setting, marked as R after the space group symbol)
2. a=b≠c, α=β=90° and γ=120° (hexagonal setting, marked as H after the space group symbol)
The first one is mostly used in the old publications, while now the second one is preferred. You can transform one setting into another for example with PowderCell.
As Alexander pointed out, there are two possible unit-cell choices. I am not familiar with High Score Plus, but I assume that this software is also able to deal with the rhombohedral unit cell setting. However, there should be an additional parameter where you can define the unit-cell choice, i.e. "1" or "2". Default value is possibly "1" which needs to be changed to "2".
The other option Alexander already told you: change into the other unit-cell description.
U cant do refinement with Rhombohedral in HSP, it will transform to Hexagonal setting. You could use HSP tool to transform back to Rhombohedral setting.
One os these seminars will specifically answer the question and others are useful for general usage:
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W20200529XRD
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W20200611XRD
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W20200702XRD?
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W20200728XRD.html
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