[Wien] After supercell, add impurity... x sgroup change space group

[Peter Blaha]

It is VERY important to check which In atoms you replace by Al.
View your structure and check: Did you cluster the Al on one side of the 
supercell ?  Did you introduce a "layered" like distribution ? ....

Most likely you want a "random" substitution, without any ordering 
(otherwise experiment might have found some order).

Most likely, the "ideal" randomly substituted structure will even have 
P1 spacegroup, i.e. all symmetry operations are lost (at least for a 
larger supercell).

PS: Experiment measures an "average structure", and therefore find a 
high symmetry SG. They put on the same position half a In and half a Al 
atom.
Of course, this is not reality.

Am 24.01.2021 um 21:31 schrieb Serhat Ayık:
> Dear Wien2k users,
> In my original struct file, I have (B Lattice) 3 non equiv. atoms 
> (Chemical form: AgInS2), space group 122_I-42d, and 8 number of symmetry 
> operations.
> I do 2x2x2, P lattice type supercell and I have 48 non equiv. (16 Ag, 16 
> In, 16 S) atoms. I want chemical form like AgAl(0.5)In(0.5)S2. I am 
> replacing 8 In atoms with 8 Al atoms. Finally, I have 16 Ag, 8 Al, 8 In 
> and 16 S in struct file.
> Then, I do
> - x nn (nn-bondlength factor:2)
> copy case.struct_nn to case.struct. (After this step, I have 7 atoms "2 
> Ag, 1 Al, 1 In, 3 S" in case.struct)
> - repeat x nn
> -  x sgroup
> warning: !!! Number of inequivalent atoms has changed. !!! Old value= 48 
> New value= 7 warning: !!! Unit cell has been reduced.
> sgroup found: 17 (P 2 2 21)
> 
> I think the space group shouldn't change.
> Is it true that the space group changes? Or am I making a mistake somewhere?
> 
> Regards
> 
> 
> 
> 
> 
> 
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> SEARCH the MAILING-LIST at:  http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
> 

-- 
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at
-------------------------------------------------------------------------