[Wien] supercell

[Peter Blaha]

I don't know if your method is correct, since I don't know your method.

But:
 >  > I want to dope an element Y into the inverse spinel structure AB2O4.  It has spacegroup 227 Fd-3m.  However, Wien2k led me to use spacegroup 74 Imma with B lattice 
for this
 >  > structure, because it requires use of non-equivalent atoms.

Already this statement makes me suspicious. You have to use SG 227 ! But remember: there are 2 different "settings"
of this SG and you have to enter the positions compatible with the setting with inversion symmetry.
Study the spacegroups (see the link to the Bilbao-server)

I suggest you start out with elemental Si and try to setup this structure correctly.

Once you have your spinel with SG 227, you run  supercell.

You have to think how large your supercell should be (how many atoms you want to have). Typical
values range from 32 to 128 !!!
So if your original   F-centered cell has 7 atoms (or 14 ? I can't remember exactly ...) you can
run supercell:
1x1x1, P-lattice. This gives 4x7 =28 atoms (which is very small). Then you would eventually
split a position and introduce the dopant.

2x2x2, F-lattice: 8+7=56 atoms is a bit better
2x2x2, B-lattice: 16x7 atoms, pretty good ...
2x2x2, P-lattice: 32x7=224 atoms:  very good...

If your original cell has more atoms (14) the procedure is very similar, but of course you would stop earlier.


Am 09.01.2013 23:11, schrieb Mohamed ouaissa:
> Dear Peter,
>
> Thanks, but can you tell me if my method to dope a structure is correct?
>
> In other words, I have 74 Imma with B lattice, so select B lattice in StructGen to split positions and add atoms, then use sgroup to find the new structure (12 C2/m).
>
> Is it possible to tell me what i should do exactely?
>
> Thanks in advance for your response.
>
> Mohamed
>
>
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> *De :* Peter Blaha <pblaha at theochem.tuwien.ac.at>
> *À :* A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
> *Envoyé le :* Mercredi 9 janvier 2013 7h16
> *Objet :* Re: [Wien] supercell
>
> At www.wien2k.at you can find the lecture note of our workshop at pennstate (http://www.wien2k.at/)
>
> Checkout my "getting started" document and maybe you can then understand the meaning of P,B or F
> in supercell.
>
> Am 09.01.2013 00:27, schrieb Mohamed ouaissa:
>  > Dear wien2k users,
>  >
>  > I want to dope an element Y into the inverse spinel structure AB2O4.  It has spacegroup 227 Fd-3m.  However, Wien2k led me to use spacegroup 74 Imma with B lattice for this
>  > structure, because it requires use of non-equivalent atoms.  To dope element Y in place of element A, for example A1-xYxB2O4 with different values of x , I use supercell
>  > input 1, 1, and 1 for number of cells in x, y, and z direction, and shift of atoms (0, 0, 0).  Since my the starting lattice is B, so I used a target lattice of B.  Then, I
>  > split element A having one non-equivalent position into two non-equivalent positions (for element A and Y) using StructGen. Finally, after running sgroup, it gives me a
>  > structure with spacegroup 12 C2/m having CXZ lattice.  Does someone know if this is the correct procedure?  Is it correct to use B as the target lattice, or should the P
>  > lattice be used to split the 4e site for spacegroup 51 Pmma having P lattice?
>  >
>  > What about if i will use a supercell 2, 1, and 1 or 2, 2, and 1 or 2, 2, and 2 ??
>  >
>  > Thanks in advance for your response.
>  >
>  > Mohamed Ouaissa
>  >
>  >
>  >
>  >
>  > _______________________________________________
>  > Wien mailing list
>  > Wien at zeus.theochem.tuwien.ac.at <mailto:Wien at zeus.theochem.tuwien.ac.at>
>  > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>  >
>
> --
> -----------------------------------------
> Peter Blaha
> Inst. Materials Chemistry, TU Vienna
> Getreidemarkt 9, A-1060 Vienna, Austria
> Tel: +43-1-5880115671
> Fax: +43-1-5880115698
> email: pblaha at theochem.tuwien.ac.at <mailto:pblaha at theochem.tuwien.ac.at>
> -----------------------------------------
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at <mailto:Wien at zeus.theochem.tuwien.ac.at>
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
>
>
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>

-- 
-----------------------------------------
Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pblaha at theochem.tuwien.ac.at
-----------------------------------------