[Wien] about the LDA+U

[jan kunes]

I do not argue that LDA+U gives the same results as LDA. I wanted to say 
that in cases like this LDA+U is not supposed to provide reasonble 
description of reality. This, I believe, is true for systems with strong 
correlations e.g. TM oxides where the filling of the d shell is close to 
integer. I do not know much about how LDA+U is supposed to work in systems 
with less strong correlation.

Jan 

On Tue, 2 Nov 2004, Yushan Wang wrote:

> but, I really find the results obtained by LDA+U are different from those
> by LDA only, although this system has a balanced spin-up and spin-dn
> structure.
> 
> yushan
> 
> On Tue, 2 Nov 2004, jan kunes wrote:
> 
> > Dear yushan,
> >
> >
> > > Dear users,
> > > does the LDA+U apply to the light transition metal. such as Ti, V, Cr and
> > > so on?
> >
> > It depends on the compound. It should work reasonably in systems, where
> > the d electrons are localized, e.g. oxides.
> >
> > , and if the spin-up and spin-dn balance well, is the LDA+U
> > > full of physical significance?
> >
> > No, LDA+U applies to ordered phase. If you have local moments as is
> > typical for localized electrons, LDA+U provides a reasonable description
> > of the ordered phase below T_c. Above T_c you still have local moments LM
> > (Curie-Weiss susceptibility), but the fluctuate in time, i.e. this is not
> > a non-magnetic NM state described by LDA or LDA+U. If you look at the
> > occupation numbers <n> there is no difference between LM and NM, in
> > both cases up=dn. The difference will be obvious from <N_up N_dn>. In NM
> > <n_up n_dn>=<n_up><n_dn> while in LM <n_up n_dn> << <n_up n_dn> due to
> > Coulomb repulsion (LDA+U however can not capture this behavior since it is
> > static method).
> >
> > Jan
> >
> >
> >  > > yushan
> > >
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