[DFTB-Plus-User] Hubbard correction in DFTB

[Gergely Juhasz]

Oh, I see. That clears up my misunderstanding.
Thank you very much,
Gergely

On Thu, Aug 16, 2018 at 11:53 PM Bálint Aradi <aradi at uni-bremen.de> wrote:

> Dear Gergely,
>
> There are two different 'U' values in DFTB:
>
> * The U values in the SK-files (usually called Hubbard Us), which
> determine the r->0 limit of the SCC-interactions. They are calculated
> from ab-initio atom calculations as second derivative of the atom energy
> with respect of the occupation of the highest occupied orbital (chemical
> hardness of the atom). They are not user tunable parameters and should
> left unchanged.
>
> * Additionally, you may add a +U type term to your Hamiltonian as in
> LDA+U. It adds orbital-dependant local contributions (when using the
> fully localised implementation) to the Hamiltonian based on the on-site
> block of the dual-density matrix. The coupling constant (U-J) is user
> tunable, and is often used (similar to ab initio programs) to achieve a
> certain property (right band gap, linearity of the energy with respect
> of occupation, etc.)
>
> The relevant keyword is OrbitalPotential, and the DFTB+ manual contains
> a trivial example and some references about the method.
>
>   Best regards,
>
>   Bálint
>
> --
> Dr. Bálint Aradi
> Bremen Center for Computational Materials Science, University of Bremen
> http://www.bccms.uni-bremen.de/cms/people/b-ar
>
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