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 ?gaux en droits. Les distinctions sociales > > ne peuvent ?tre fond?es que sur l'utilit? commune > > - Article 2 - Le but de toute association politique > > est la conservation des droits naturels et > > imprescriptibles de l'homme. Ces droits sont la libert?, > > la propri?t?, la s?ret? et la r?sistance ? 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 ?gaux en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur l'utilit? commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? 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>