[Pw_forum] Constrained occupation

[Gabriele Sclauzero]

Dear Jie,

    The only result that you will get by insistently repeating your question every few hours is to irritate the other users, hence the probability that you get an answer will drop considerably. Also consider that from an european point of view you asked your question in the middle of the night.


Il giorno 06/nov/2010, alle ore 03.50, Jie Jiang ha scritto:

> Dear All,
> 
> Again, is it possible to do occupation constraint DFT calculations with PWscf?
> Can the option 'occupations=from_input' do that?

This option is to fix occupation, not to constrain them, and it is usually used to force an electronic configuration for an atom or a molecule computed with plane waves in a big box.

Constrained DFT is another thing, in my opinion, and I don't think it has been implemented in QE so far.

> 
> If not, is there any suggestion on where and how to modify to include
> this function.

You should first read the relevant literature (if I remember well, Dederichs and Bluegel were the first to apply it), then devise an algorithm and implement it. If you are really willing to do so, I think you'll get some help from the core developers. Anyway, I don't think it is so straightforward to do.

Regards,

GS

> 
> Thanks,
> 
> Jie   
> 
> On Fri, Nov 5, 2010 at 7:20 PM, Jie Jiang <jiejiangnc at gmail.com> wrote:
> Dear All,
> 
> Does 'occupations=from_input' mean occupations of individual states
> are fixed ?
> 
> Can I define the occupations of the highest occupied state and lowest 
> unoccupied state to be 1 and 1 to calculate the electron-hole excitation
> energy?
> 
> Thanks for any comments.
> 
> Jie
> 
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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