[Wien] GGA+U

[Pavel Novak]

there in fact is a paper of Savrasov and Kotliar, PRL 84,3670 (2000) in
which GGA+U is used. GGA+U is also used in one of A.S.Shick papers (I do
not remember the reference) and we submited recently two papers using
GGA+U.

Pavel Novak

On Mon, 22 Nov 2004, Stefaan Cottenier wrote:

>
> > I actually wonder whether there is some specific reason why there is no
> such
> > kind of " GGA+U" calculation in the literature but only LDA+U.....is this
> > maybe due to the fact that GGA is already an improvement upon LDA and
> > therefore LDA+U should take already into account  the feature of GGA
> alone?
>
> Other may correct me if I'm wrong, but I guess this is the reason: the
> "U-trick" is a rough approximation, that is not really ab-initio (you have
> to tune a free parameter). At best, one can hope for semi-quantitative
> agreement with experiment. In such circumstances, it is best to agree to
> start from the only XC-functional that can be uniquely defined: LDA (GGA's
> come in different flavours). If one would start using GGA+U, then there
> might be a correlation between the U and the type of GGA: the question
> "which U should I use" would become even more difficult to answer...
>
> Stefaan
>
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