[Pw_forum] init_london Error

Thu Jun 30 18:36:08 CEST 2011

Dear Giuseppe,

Thank you very much for the clarification. 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. They gave me
correct experimental crystal parameters as well (within 2%). But it is
definitely good to know about of them and their differences.

I have one more related question if you could clarify.

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 (which I assume will read the electronic
interaction from previously saved wavefunction information, if I run
it in the same directory as I ran SCF calculation and stored all files
in that directory). In that case, will the calculated dynamical matrix
include the interactions from vdw forces as well?

I am asking this as ph.x does not consider DFT-D2 type of interaction
(no flag for it, hopefully I will work on it) while evaluating
dynamical matrix.

Any insights will be beneficial for my knowledge as well as for future studies.

Thanks in advance.

Best Regards,
Vikas Varshney
Computational Material Scientist
Wright Patterson Air Force Base, Dayton OH

On Thu, Jun 30, 2011 at 5:12 AM, Giuseppe Mattioli
<giuseppe.mattioli at mlib.ism.cnr.it> wrote:
>
> 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).
>> >
>> > --
>> > ********************************************************
>> > - 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>
>> > _______________________________________________
>> > Pw_forum mailing list
>> > Pw_forum at pwscf.org
>> > http://www.democritos.it/mailman/listinfo/pw_forum
>
>
>
> --
> ********************************************************
> - 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>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>