[DFTB-Plus-User] DFTB+U

[Ben Hourahine]

Hello Toufik,


the underlying SCC-DFTB model uses Hubbard U values, but not in the way
that DFTB+U applies this. The CustomisedHubbards modifies this.


For DFTB+U calculations, the OrbitalPotential keyword specifies the U
values and the type of model (FLL is the common one).


The reason for the separation, is that in SCC-DFTB, the U values are
closely related to the chemical hardness of the atoms and hence the
GGA-like exchange correlation in the model. The U values for DFTB+U are
more empirical (depending on your specific approach to LDA+U methods)
and so is set separately from the underlying model.


Regards


Ben


On 22/06/2021 12:21, toufik esssakhri wrote:
> CAUTION: This email originated outside the University. Check before
> clicking links or attachments.
> Dear all,
>
> I want to perform DFTB+U calculations. In the manual I found two
> keywords that I can use for it but I can not understand the difference
> Could someone give more explanations about the difference between
> "CustomisedHubbards"  and "OrbitalPotential"? Which one is more
> suitable for DFTB+U calculations?
>
> Thank you
> Toufik
>
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         Dr. B. Hourahine, Senior lecturer
            SUPA, Department of Physics,
             University of Strathclyde,
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