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["Cote Michel" <michel.cote@umontreal.ca>]

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
>