[Wien] A question regarding the calculated values of the DOS - a single unit cell vs a supercell

[Stefaan Cottenier]

You seem to be counting the number of inequivalent positions, rather 
than the total number of atoms in the unit cell. Count the number of 
position lines in your case.struct (or sum the MULT numbers). This will 
probably solve most of your problem.

Furthermore, the DOS of a supercell inevitably will show the results of 
backfolding (search the mailing list archive, or google for 'band 
structure backfolding'). That might spoil your comparison too, to some 
extent.

Stefaan


On 22/09/2011 9:24, Qiwen YAO wrote:
> Dear Wien2k users, I have a question regarding the calculated values
> of the DOS - a single unit cell vs a supercell please:
>
> I have a unit cell with 4 atoms in a single cell for the compound of
> Sr2CoO4, and I was doing the DOS calculation (spin polarized
> calculation) on it  - and the converged total DOS at EF level was
> about 2 states/eV spin up and 3 stats/eV spin down (so this is a spin
> polarized system).
>
> Then I do a 2x2x1 supercell calculation for the same structure (but
> for a Nd doped compound: Sr1.5Nd0.5CoO4 - one of the Sr out of four
> was replaced by one Nd - so a supercell is necessary in this case).
> After the initialization WIEN2k turn the structure into a 13 atom
> cell for calculation. Here comes the thing confuses me: the
> calculated total DOS results in the EF level for this supercell seems
> to be too high - with about 10 states/eV spin up and 30 states/eV
> spin down.
>
> I was asking someone about this and I was told that I need to divide
> the resulted DOS values by 4 to get the actual result for a single
> cell from the supercell calculation - is this correct? But the unit
> of the DOS is states/eV - would this means it is not atom-number
> dependent?  If I need to divide it by a number should this number be
> (13/4) instead of 4 - because WIEN finally calculates the cell as a
> 13-atom cell, not a 12-atom cell?
>
> I am looking forward to any respond on this - I know this seems to be
> a simple question for many of you but I am new to Wien2k, sorry for
> taking up your time on this. But I do want to be clear in this.
>
> Thank you and regards,
>
> Qiwen
>
> **********************************************************
>
> Dr QiWen YAO JSPS Fellow Multifunctional Materials Group Optical and
> Electronic Materials Unit Environment and Energy Materials Research
> Division
>
> National Institute for Materials Science
>
> 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan Phone:
> +81-29-851-3354, ext. no. 6482, Fax: +81-29-859-2501
>
> **********************************************************
>
> _______________________________________________ Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien