[Wien] How to set the occupation number in Wien2k?

[Peter Blaha]

In an GGA+U calculation you can manipulate case.dmatup/dn and specify 
occupations as you like. (Note, this will most likely also involve 
off-diagonal elements because you need to form "real-spherical 
harmonics" out of the complex dmats).

Then run    x orb -up/dn    (producing case.vorbup/dn

runsp -orbc

makes a constraint calculations with fixed orbital potentials. However, 
there is no guarantee that this leads then the the desired occupancy !!
All it does is: it will lower the potential of the occupied orbitals and 
if this shift is large enough, it may work.

after scf  you can use

x lapwdm -up/dn  to create new case.damt (and check if this has the 
desired occupation). Eventually afterwards you continue with

runsp -orb

to see if this configuration remains (meta-)stable or if the dmats 
change back to something differently ...

--------------------
Alternatively, you can treat 4f electrons as "core" with a specific 
number of 4f electrons. I think there is some description by P.Novak on 
the web for this. (I would not recommend this)

On 07/16/2015 09:55 AM, Bin Shao wrote:
> Dear all,
>
> I want to calculate an excited state of Er ion and need to set the
> occupation number of f electron. Can we achieve it in Wien2k? Since the
> orbital occupations are expressed into a spherical harmonics basis, can
> we set them manually and do a constrained DFT calculation?
>
> any comments will be appreciated and thank you in advance,
>
> Best regards,
>
> Bin Shao
>
> --
> Bin Shao
> Postdoc
> Department of Physics, Tsinghua University
> Beijing 100084, P. R. China
> Email: binshao1118 at gmail.com <mailto:binshao1118 at gmail.com>
>
>
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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