I am studying on the occupation of particular activator (which is coordinated with 9 and 7 oxygen atoms) in a crystal host where the author mentioned this: 6c site in the 1-fold axis and 2b site in the 3-fold axis. I would like to ask how can we determine the number of fold and also what is mean by 6c and 2b site?
Thank you.
Dear Khai Shenn Lau ,
I do believe it is related to your crystallographic space group rather than number of coordinations. From your space group, you can determine symmetry elements (fold, mirror, etc) and wickoff positions of your group (6c, 2b). Maybe you can provide the space group you are working with for clearer explanation ?
You do not need to redetermine all the symmetry elements, as everything is already reported in the international tables of crystallography, with explanations.
I attached an example of the P2 space group, involving 2-fold axis (represented with the black "dot".
In the P2 example attached, if you have an atom at 0,0,0 it will be on a 2-fold axis, and a 1a site.
a 2-fold rotation operation moves the object by (360/2) ° = 180 ° around the fold axis.
a 3-fold(C3) rotation operation moves the object by (360/3) ° = 120 °
and so on.. It just describe equivalent positions in your structure.
Sites are mostly sorted by multiplicity, and then a letter is associated to them (starting from "a" at the lower multiplicity, and then b, c, d, and so on).
I would recommend getting through a crystallography course as their is really too much things to explain if you are not confident with crystallography. I would recommend courses from B. Grenier : https://doi.org/10.1051/epjconf/20122200006
However you do not really need to put such information in a publications if you are not confident with them, tables of crystallography is sufficient for most readers.
Hope it helps,
Kind regards,
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