[Wien] Fwd: Query regarding the structure generation

[Peter Blaha]

As you wrote, the position Pb/Rb (8k) is an averaged postion of mixed Pb 
and Rb occupation due to disorder.

In a simulation, you cannot have "mixed positions (or high symmetry, but 
you must lower the symmetry.

To create such a structure, enter all position as usually, but for the 
mixed Pb/Rb 8k position, just enter it as pure Pb position.

After this, of course your stoichiometry is wrong. So you must split 
this position into 2, and occupy the proper number of positions with Rb 
instead of Pb. Select the specific Rb positions as "randomly" as 
possible, i.e. make sure they are not "clustered" on one side of the 
cell, or do not form a single layer, ...

nn, sgroup and symmetry will find the proper equivalency and of course 
the resulting space group will be different from the random experimental 
structure.

PS: Eventually you even need a supercell to make an even better "random 
structure".

Am 30.01.2021 um 17:10 schrieb Subhasis Panda:
> 
> Dear experts,
> 
> I was trying to generate the structure for Rb6Pb5Cl16.  It consists of 
> atoms (multiplicity wyckoff letter) Rb1 (4h), Rb2 (4g), Rb3 (2a), Pb1 
> (4e), Pb/Rb (8k), Cl1 (16l), Cl2 (8j), Cl3 (4g), Cl4 (4f) and space 
> group is P4/mbm. If I generate this structure with this information I am 
> getting Rb10Pb12Cl32. I have tried to split the Pb/Rb (8k) into Pb (6 
> no) and Rb (2 no), found that nn generates a new struct file and space 
> group changes to c2/m.  I am not understanding where I am wrong. Looking 
> forward for some help.
> 
> 
> 
> 
> Thank you in advance.
> 
> 
> -- 
> With regards
> Anupriya Nyayban
> Ph.D. Scholar
> Department of Physics
> NIT Silchar
> 
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