[Pw_forum] init_london Error

[Giuseppe Mattioli]

Dear Vikas
No, it does not. The "london" flag activates a semiempirical point-to-point 
contribution which "simulates" dispersion interactions but does not modify 
the wavefunctions (often referred to as DFT-D2). The vdW-DF is an improved 
LDA correlation functional which accounts for long range electronic 
interactions; vdW interactions arise "naturally" as contributions to the 
Hellmann-Feynman forces. Currently, there is not a "best choice" among DFT-D2 
and vdW-DF. DFT-D2 provides the best results in the case of graphite 
stacking. vdW-DF behaves better in the case of molecule-surface interactions. 
You could test both.
Yours

Giuseppe


On Friday 24 June 2011 15:39:50 Vikas Varshney wrote:
> Dear Giuseppe,
> Thanks for your email. Although, I finished my calculations successfully by
> .london. flag, I wanted to ask if input=dft="vdw-df" does the same thing?
>
> Best Regards,
> Vikas
> On Thu, Jun 23, 2011 at 5:52 AM, Giuseppe Mattioli <
>
> giuseppe.mattioli at mlib.ism.cnr.it> wrote:
> > Dear Vikas
> > You can also use the ab-initio implementation of vdW forces by switching
> > on the input_dft="vdw-df" flag.
> > HTH
> > Giuseppe
> >
> > On Tuesday 21 June 2011 16:40:02 Vikas Varshney wrote:
> > > Dear All,
> > >
> > > I am trying to relax my WS2 unit cell structure using vc-relax (using
> > > PBE pps) and I want to include disperson corrections to it. So, I tried
> > > using the london flag = .true. However, on starting my job I got an
> > > error
> >
> > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >%%
> >
> > >%%% from  init_london  : error #         1
> > >      atom W   not found
> >
> > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >%%
> >
> > >%%%
> > >
> > > After going through mm_dispersion.f90, I found that the vdw_radius and
> >
> > c_6
> >
> > > parameters are given for first 54 atoms only (which corresponds to
> > > first
> >
> > 5
> >
> > > periods of periodic table). Tungsten (W), with atomic number of 74 is
> > > in 6th period.
> > >
> > > I emailed Prof. Stefan Grimme (author of the references that are
> >
> > mentioned
> >
> > > in mm_dispersion.f90) if anything was further pursued. He replied
> > > mentioning that they have approached this problem further and referred
> > > me to his website,
> > >
> > > http://toc.uni-muenster.de/DFTD3/
> > >
> > > and told me that this has already been implemented into major QM codes.
> > >
> > > Mentioning that, I have few questions.
> > > 1. I wanted to ask if QE has incorporated the additions DFT-D,
> > > recently. 2. Are there any other ways to incorporate dispersion
> > > interactions in calculations in DFT.
> > >
> > > Currently, I am running my simulations on 4.2 version of the code that
> > > I downloaded few months ago. I would high appreciate your insights in
> > > how should I go about solving this problem regarding dispersion
> > > interactions
> >
> > in
> >
> > > Tungsten.
> > >
> > > Looking forward for a positive reply.
> > >
> > > Best Regards,
> > >
> > > Vikas Varshney,
> > > Computational Materials Scientist,
> > > Wright-Patterson Air Force Base, Dayton-OH (USA).
> >
> > --
> > ********************************************************
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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)
> >    Tel + 39 06 90672836 - Fax +39 06 90672316
> >    E-mail: <giuseppe.mattioli at ism.cnr.it>
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-- 
********************************************************
- Article premier - Les hommes naissent et demeurent
libres et ègaux en droits. Les distinctions sociales
ne peuvent être fondèes que sur l'utilitè commune
- Article 2 - Le but de toute association politique
est la conservation des droits naturels et 
imprescriptibles de l'homme. Ces droits sont la libertè,
la propriètè, la sùretè et la rèsistance à l'oppression.
********************************************************

   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
   v. Salaria Km 29,300 - C.P. 10                
   I 00015 - Monterotondo Stazione (RM)          
   Tel + 39 06 90672836 - Fax +39 06 90672316    
   E-mail: <giuseppe.mattioli at ism.cnr.it>