[Pw_forum] How to fixed the valence of atom

[Nicola Marzari]

Dear Yuki-san,


prompted by your question, and thanks to kind help from David O'Regan,
I've written a short tutorial on this here (see oxidation states):
http://theossrv1.epfl.ch/Main/Tutorials

In a nutshell, it's very doable, albeit with some scripting to streamline
the extra calculations needed.

	
			nicola


On 11/06/2014 06:31, 奥野幸洋 wrote:
> Dear PWSCF users.
>
> I'm now try to fixed the valence of one atom in the cell.
>
> For example, how we impose one of the Nb atom as (+4) valence
>
> (one electron is localized in Nb atom   Nb(+5) is ideal condition )
>
> in the crystal.
>
> I tried to use  constrained_magnetization = 'atomic'
>
> with statring_magnetization  like below,
>
> (Here atom index 2 is Nb atom which I set as valence (+4, one electron
>
> localized in Nb atom, 3 is Nb atom with ideal +5 valence )
>
>     starting_magnetization(1) = 0.0
>      starting_magnetization(2) = 1.0
>      starting_magnetization(3) = 0.0
>      starting_magnetization(4) = 0.0
>      starting_magnetization(5) = 0.0
>      lda_plus_u =.TRUE.
>      lda_plus_u_kind = 0
>      Hubbard_U(2)=4.0
>      Hubbard_U(3)=4.0
>      tot_charge = -1.0
>      tot_magnetization = 1.0
>      constrained_magnetization = 'atomic'
>      lambda = 1.0
>
> But, the results was some of Nb atoms has a little excess electron (,
> but smaller than one ), and I couldn't get +4 Nb which I aimed to
> make.
>
> How to treat to impose the localized electron in one of the atoms
>
> in crystals.
>
> If I can get reply, I'm very happy.
>
> Sincerely,
>
> Yukihiro Okuno.
>
> --
> 　
>
>
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-- 

----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL