[Pw_forum] aligning eigenvalues for isolated molecules/atoms

[Giuseppe Mattioli]

Dear Davide

Yes, the procedure is correct, and you can easily compare the results  
with those obtained in a GTO framework. If you neglect/minimize basis  
sets issues, pseudopotentials issues, numerical noise, etc., you  
generally obtain close eigenvalues in PW/GTO frameworks, using the  
same xc functional.

> Then I should have something more or less comparable amongst  
> different isolated system and in which the HOMO is always negative  
> and the LUMO is either very close to 0 or positive.

This depend on the functional, of course... There are tons of papers  
on ionization energy, electron affinity and related DFT errors.

Best
Giuseppe

Quoting Tiana Davide <davide.tiana at epfl.ch>:

> Dear all
>
>
> I would like to check I am doing the correct things.
>
>
> I need to compare the eigenvalues of some atoms and molecules.
>
> I am following this procedure:
>
>
> 1) pw in a cube cell bigger enough to exclude any interaction with  
> its neighbours.
>
> 2) adding the "assume_isolated='makov-payne'" option in the input
>
> 3) add the "Corrected vacuum level" found at the bottom of the  
> output to each eigenvalue.
>
>
> Then I should have something more or less comparable amongst  
> different isolated system and in which the HOMO is always negative  
> and the LUMO is either very close to 0 or positive.
>
> This is what I would expect using LCAO programs like Gamess or  
> Gaussian, can I expect something similar using pw and mp correction?
>
>
> Best Regards
>
> ?Davide


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    Giuseppe Mattioli
    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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