The ABINIT Users Mailing List ( CLOSED )

[Fabien Bruneval <fabien.bruneval@polytechnique.fr>]

Dear all,
For what concerns the use of TDDFT of solids there have been a lot of
progresses that not justify the sentence: tddft does not work for solids.
A new theoretical approach, based on the link between many-body
perturbation theory and time dependent density functional theory, has
appeared, and the preliminary results are very encouraging.
The main references are PRL 91, 56402 (2003) and PRL 91, 256402 (2003).
Moreover a thesis is available on this subject at
http://theory.polytechnique.fr/people/sottile/Tesi_dot.pdf .
In particular for what concerns optical and electron energy loss
spectra of semiconductors and insulators, these approaches seem
to work very well. I'm not directly connect with this, but 
I will only follow the developements of the method, because
I'm interested in this problems like you are.

Fabien






Masayoshi Mikami wrote:

> Hello,
>
> I came across the following Ph.D thesis (related to "ADF-BAND").
> I just thought that it might be interesting to those who are concerned.
> So please let me share the information with the forum ML subscribers.
>     "Time-dependent density functional theory for periodic systems"
>     Freddie Kootstra
>     http://www.scm.com/Doc/ft439.pdf
>
> Best wishes,
> Masayoshi
>
> On 2004/02/18, at 23:20, Cote Michel wrote:
>
> > Hello Axel,
> >
> > As far as I know, TDDFT does not quite work for extended systems at 
> > present. The problem is in the functional used to get fxc. The 
> > implementation in Abinit presently is TDLDA (or TDGGA I think) and 
> > those have been shown to have not effect on the Kohn-Sham 
> > eigenvalues, so the correction is nil. In short, we have to wait for 
> > the development of a good functional.
> >
> > It will be nice of you to share your results on the supercell of Si 
> > but I expect that you will get no change on the value of the energy gap.
> >
> > Michel
> >
> > ***************************************************************
> >   Michel Cote                          tel: +1 (514) 343-5628
> >   Professeur adjoint                   fax: +1 (514) 343-2071
> >   Département de physique
> >   Université de Montréal
> >   C.P. 6128, succ. Centre-ville
> >   Montréal (Québec) H3C 3J7          Michel.Cote@umontreal.ca
> >   Canada              http://www.phys.umontreal.ca/~michel_cote
> > ***************************************************************
> >
> >
> >
> >
> >
> > > -----Message d'origine-----
> > > De : avdw@northwestern.edu [mailto:avdw@northwestern.edu]
> > > Envoyé : 18 février, 2004 09:07
> > > À : forum@abinit.org
> > > Objet : [abinit-forum] Time Dependent DFT in extended solids?
> > >
> > >
> > > Hi everyone,
> > > is it possible to obtain excitation energies with TDDFT in extended
> > > solids with abinit?
> > > I undertstand that only single k-point calculations are implemented at
> > > this point,
> > > but using a supercell can easily take care of that restriction.
> > > I am mostly concerned with the requirement of specifying the
> > > "center" of
> > > the molecule, which is impossible for an extended solid.
> > > However, I tested various "boxcenter" values and obtained the
> > > same excitations
> > > energies in Si, as far as I can tell.
> > > So, it looks like as long as I do not need the "oscillator strengths",
> > > using a supercell works fine.
> > > I am correct in my assumption?
> > > Thanks,
> > > Axel