[Pw_forum] Spectra from GW and TDDFPT

[Giuseppe Mattioli]

Dear Jiayu
Yes, it is. You can perform TDDFPT calculations by using the gamma point, 
nspin=1 and fixed occupations (no smearing). There are no theoretical 
limitations regarding k-points, but they are currently not implemented.
Yours
G.

On Thursday 14 April 2011 11:58:34 jiayudai wrote:
> Dear Giuseppe,
>
> I think the current TDDFPT can only work without spin polarization, is it?
> Besides, i do not know is there any limitation in theory to deal with more
> k_points and metallic case? In my test, it can not deal with the molecule
> such as NO2, since it needs the smearing method in the scf calculations.
>
> Thanks.
>
> Jiayu
>
>
> From: Giuseppe Mattioli <giuseppe.mattioli at mlib.ism.cnr.it>
> Subject: Re: [Pw_forum] Spectra from GW and TDDFPT
> To: PWSCF Forum <pw_forum at pwscf.org>
> Message-ID: <201104131649.52909.giuseppe.mattioli at mlib.ism.cnr.it>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Jiayu
> Yes, it is. With only one additional warning: the TDDFPT code works only at
> Gamma (and fixed occupations). It is not designed to deal with periodic
> systems where you need k-points, but (in my experience) it works well with
> molecules.
>
> On Wednesday 13 April 2011 15:20:59 jiayudai wrote:
> > Thanks for your recommendation and reply, mohsen and Giuseppe. So,
> > Giuseppe, i understand what 's your meaning is that the GWW and TDDFPT in
> > QE distribution (4.3) can be used for different purposes, but they are
> > both accurate in their fields. In addition, they both have the advantage
> > of efficient computation speed becuase they used different method from
> > the tranditional methods. Is it?
> >
> > Thanks again.
> >
> > Jiayu
> >
> > > Pw_forum at pwscf.org
> >
> > From: Giuseppe Mattioli <giuseppe.mattioli at mlib.ism.cnr.it>
> > Subject: Re: [Pw_forum] Spectra from GW and TDDFPT
> > To: pw_forum at pwscf.org
> > Message-ID: <201104131432.02080.giuseppe.mattioli at mlib.ism.cnr.it>
> > Content-Type: text/plain; charset="utf-8"
> >
> >
> > And, practically speaking, you can obtain corrected (i.e., quasiparticle)
> > eigenvalues by using GWW, and absorption spectra by using turbo_lanczos,
> > that is, the GW and TDDFPT current implementations that you find embedded
> > into the QE (4.3) distribution. Within the above limitations, the
> > computational cost of both methods can be considered rather low.
> > HTH
> >
> > Giuseppe
> >
> > On Wednesday 13 April 2011 13:59:50 mohsen modaresi wrote:
> > > Dear Jiayu Dai,
> > > Prof. R. Godby is one of the most famous scientist who worked on
> > > many-body theory. i think this lecture should be help full for you.
> > > {Many-Body Theory and DFT / TDDFT
> > > Rex Godby"
> > > http://docs.google.com/viewer?a=v&q=cache:gBMHk9QaO3cJ:www.tddft.org/TD
> > >DF T2
> > > 006/2006tddft/docs/school/Godby.pdf+TDDFT+and+GW&hl=en&pid=bl&srcid=ADG
> > >EE Siq
> > > 9Au0dGZsFvyPUtLL9nEaPg44xzN8NzkJiiguvyAdyTFUpucP8XOKWMyrKammwPLMDfQZncm
> > >tg oh8
> > > NA-PFsRKaUxsRnrdbFId7a7dW2mkkOHqrr4TFgpalZC775KF1njtbF4p&sig=AHIEtbTLv5
> > >Xg Sx5 m0wfXO3sMV7vzJlgOtg&pli=1
> > >
> > > Hope it helps,
> > >
> > >
> > > 2011/4/13 jiayudai <daijiayu at nudt.edu.cn>
> > >
> > > > Dear users,
> > > >
> > > > It is well known that GW method can give much more accurate band gap
> > > > since it considers many body interaction, and thus it can give more
> > > > accurate optical properties. What i am thinking is that what's the
> > > > difference between the optical properties from TDDFPT and GW. I mean,
> > > > TDDFPT has the same accuracy as the GW method? or what's the
> > > > advantage of TDDFPT over the GW except the computationl cost?
> > > >
> > > > Thanks a lot.
> > > >
> > > > Jiayu
> > > >
> > > >
> > > > -------------------------------------------
> > > > Jiayu Dai
> > > > Department of PhysicsNational University of Defense Technology,
> > > > Changsha, 410073, P R China
> > > > -----------------------------------------



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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
   v. Salaria Km 29,300 - C.P. 10                
   I 00015 - Monterotondo Stazione (RM)          
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