[Wien] Interstitial chrge in Supercell

[David Holec]

Dear Alpa,

According to the labels I would say that the reported interstitial
charge is per the whole unit/supercell. Thus, if you have for example
2x2x2 supercell, you should expect ~8x higher interstitial charge than
in the unit cell case. This seems to be also your case, 8 * 1.3513408e
= 10.81e which is quite close to the value reported for the supercell.

A question for more experience Wien2k users: why we do get a
difference in the charge on Mg (and not for O) between the unit cell
and supercell calculations? I assume the Rmt were the same in both
cases. Is this due to some limitations of the numerical solution?
Which parameters would be crucial (Rmt*Kmax, l_max, some parameters of
basis functions, etc.) in order to get the same charges on Mg (and
thus also the interstitial charge) in both cases?

Thanks,
David

2009/5/21 alpa dashora <dashoralpa at gmail.com>:
> Dear Wien2k users,
>
> I am trying to learn the super cell calculation using Wien2k code. I have
> tried the super cell calculation for MgO. I have successfully made the super
> cell. I have also compared the band gap of super cell calculation and simple
> calculation, both are nearly equal. In case of charge density in case.scf
> file, charge of Mg and O atom in supercell calculation is same as obtained
> in the simple calculation but the interstitial charge is increased with
> large amount.
>
> In MgO.scf:
>
>        CHARGES OF NEW CHARGE DENSITY
> :NTO  : TOTAL   INTERSTITIAL CHARGE=  1.3513408
> :NTO001: TOTAL   CHARGE IN SPHERE  1 (Mg) = 10.4017583
> :NTO002: TOTAL   CHARGE IN SPHERE  2  (O) =  8.2468982
>
> In super.scf
>
>        CHARGES OF NEW CHARGE DENSITY
> :NTO  : TOTAL   INTERSTITIAL CHARGE= 11.0052414
> :NTO001: TOTAL   CHARGE IN SPHERE  1 (Mg) = 10.3769756  Multiplicity=1
> :NTO002: TOTAL   CHARGE IN SPHERE  2 (Mg) = 10.3769756  Multiplicity=1
> :NTO003: TOTAL   CHARGE IN SPHERE  3 (Mg) = 10.3769651  Multiplicity=6
> :NTO004: TOTAL   CHARGE IN SPHERE  4 (O)  =  8.2472885  Multiplicity=6
> :NTO005: TOTAL   CHARGE IN SPHERE  5 (O)  =  8.2474031  Multiplicity=6
>
> Please tell me, why the interstitial charge is very high in both the cases?
> --
> Alpa Dashora
>
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