[Pw_forum] init_london Error

[Giuseppe Mattioli]

Dear Vikas
A final remark: 

> I am using GGA functionals
> for my relaxation. So, as you mentioned vdw-DF is improved for LDA
> type of functionals, I will stick with the london option.

The vdW-DF functional is not a simple LDA xc functional. It contains a 
long-range LDA correlation contribution. Some lines extracted from the 
Modules/funct.f90 file may help to explain:

  !              "pz"    = "sla+pz"            = Perdew-Zunger LDA
  !              "pbe"   = "sla+pw+pbx+pbc"    = PBE
  !              "revpbe"= "sla+pw+rpb+pbc"    = revPBE (Zhang-Yang)
  !              "vdw-df"= "sla+pw+rpb+vdw"    = vdW-DF
  !
  ! Exchange: 
  !              "sla"    Slater (alpha=2/3)             
  !
  ! Correlation: "noc"    none                           
  !              "pz"     Perdew-Zunger                  
  !              "pw"     Perdew-Wang                    
  !
  ! Gradient Correction on Exchange:
  !              "pbx"    Perdew-Burke-Ernzenhof exch   
  !              "rpb"    revised PBE by Zhang-Yang      
  !
  ! Gradient Correction on Correlation:
  !
  !              "pbc"    Perdew-Burke-Ernzenhof corr    
  !
  ! Van der Waals functionals
  !              "nonlc"   none                           
  !              "vdw1"    vdW-DF1                       
  !              "vdw2"    vdW-DF2                       
  !
  ! References:
  !              pz      J.P.Perdew and A.Zunger, PRB 23, 5048 (1981) 
  !              pbe     J.P.Perdew, K.Burke, M.Ernzerhof, PRL 77, 3865 (1996)
  !              pw91    J.P.Perdew and Y. Wang, PRB 46, 6671 (1992)
  !              revPBE  Zhang and Yang, PRL 80, 890 (1998)
  !              vdW-DF  M. Dion et al., PRL 92, 246401 (2004)
  !                      T. Thonhauser et al., PRB 76, 125112 (2007)

Yours
Giuseppe

On Friday 01 July 2011 09:49:54 Stefano de Gironcoli wrote:
> vdW-DF is not yet implemented in the DFPT part.
> we are working on that,
> stefano
> -
> Stefano de Gironcoli - SISSA and DEMOCRITOS
>
> On 07/01/2011 09:45 AM, Paolo Giannozzi wrote:
> > On Thu, 2011-06-30 at 12:36 -0400, Vikas Varshney wrote:
> >> Lets say for my system of interest, I want to use LDA functionals with
> >> vdw-DF setting (which will modify the wavefunctions) and run an SCF
> >> calculation on a previously relaxed geometry. Then, I do the phonon
> >> dispersion calculation (...). In that case, will the calculated
> >> dynamical matrix include the interactions from vdw forces as well?
> >
> > only in part, because you will start from vdw-aware wavefunctions,
> > but you will miss the vdw term in the second derivative of the
> > exchange-correlation functional. I just heard rumors that this
> > will be soon implemented, though
> >
> > P.
>
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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
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