The ABINIT Users Mailing List ( CLOSED )

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

Dear George,

The GW approximation is indeed implemented in Abinit. However, in Abinit 
it is just meant to calculate the electronic band structure in a 
periodic system.

In principle, the GW approximation can be used to calculate total 
energies and forces, but the calculations are so cumbersome that only 
atoms have been calculated so far (see the work of R. van Leeuwen for 
instance).

If you really want to treat big systems like nanotube + amino acid, you 
can forget about the GW approximation and turn to simpler methods.

I hope to have clarified the situation.


Fabien







George Abadir wrote:
> Dear Jean-Christophe,
>                                   Thank you very much for your reply. I 
> am aware of the VDW problems with DFT. The point is that I need an 
> accurate bandstructure for the CNT. As far as I understand, the GW 
> approximation can do that and it is included in ABINIT. Could you guide 
> me to other packages that can perform the calculations within the GW 
> approximation for my problem? If not,  can ABINIT in principle do the 
> calculations may be at a large computational cost? Or will the size of 
> the supercell be prohibitive in your opinion?
>                                  Thanks alot for your help,
> Regards,
> George
>
> Jean-Christophe Charlier wrote:
>
> > Dear George,
> >
> > ABINIT is probably not the best code to investigate amino
> > acids adsorbed on carbon nanotubes because your simulation
> > will need a large supercell and lot's of vacuum in order to
> > avoid the interaction between the repeated images.
> > DFT codes based on localized basis sets (and not plane-waves
> > like ABINIT) for the expansion of the wavefunctions are probably
> > more appropriate (i.e. Siesta, Gaussian, ...).
> >
> > In addition, DFT has some problem to accurately describe weak
> > interactions such as VdW that you should observe when an amino
> > acid is adsorbed at the surface of a nanotube.
> >
> >     Regards,  
> >                 Jean-Christophe
> >
> > On 25 Oct 2007, at 06:12, georgea@ece.ubc.ca wrote:
> >
> > > Hi all,
> > >        I am a new user to ABINIT. My goal is to perform simulations  
> > > of amino acids adsorbed on carbon nanotubes. My question is: can  
> > > ABINIT perform such simulations to get the electronic properties of  
> > > the nanotube after the adsorption of the amino acid? If so, is  there 
> > > a way to visualize my input structure after building the  input file 
> > > and before actually performing the simulations?
> > >        And if not, are there other tools that can do it and have the
> > > GW approximation?
> > >        Thanks alot,
> > > Regards,
> > > George