thanks again sir
i need to know what is the AFM orders for P3m1 (156) ??? type II or III
thanks in advance
Le dimanche 26 janvier 2020 à 20:51:41 UTC+1, Gavin Abo
<[email protected]> a écrit :
the definition for the compound a=b = 3.74 A alpha = beta = 90 gamma =
120 for AFM type I : i creat superstructure x super cell target lattice H
: x =1, y = 1 , Z =2 then x sgroup, program define automatically the space
group the same of my original space group 156 without warrning
As you have described above (for Z=2), your attempt at creating a supercell has
failed as "x sgroup" collapsed the supercell structure back to the
non-supercell structure.
As mentioned on the FAQ page for supercell construction, you need to displace
an atom, change an atom, or use a special label:
http://susi.theochem.tuwien.ac.at/reg_user/faq/supercells.html
In order to keep the supercell without "x sgroup" reducing it back to the
original structure, refer to previous posts in the mailing list archive about
breaking the symmetry. A few of the many posts about that as examples are at
the three links below:
https://www.mail-archive.com/[email protected]/msg18380.html
https://www.mail-archive.com/[email protected]/msg01866.html
https://www.mail-archive.com/[email protected]/msg15517.html
but when try to do it for type II : x super cell P : x =1, y = 1 , Z =1
x sgroup could not define the space group
In section "3.12 Setting up a new case" on page 29 in the WIEN2k 19.1
usersguide [
http://susi.theochem.tuwien.ac.at/reg_user/textbooks/usersguide.pdf ], there is
the statement:
"Alternatively with the new StructGen you can specify the spacegroup and only
the inequivalent positions. The equivalent ones will be generated
automatically."
This means spacegroups in WIEN2k are defined according to the inequivalent
positions and not by the equivalent positions.
For the case above (Z=1), it is likely that "x supercell" found some equivalent
positions in the original structure and automatically added special labels to
them changing them into inequivalent positions. Thus, a supercell structure was
successfully created. If you want the supercell structure to reduce back to
the original structure, you would likely just need to remove all or some of the
special labels in StructGen before running "x sgroup".
For understanding the inequivalent and equivalent positions with WIEN2k
spacegroups, the example in the post at the following link might helpful:
http://zeus.theochem.tuwien.ac.at/pipermail/wien/2013-January/018171.html
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