Dear Giuseppe and Gabriele I agree with Gabriele that PBE-D2 gives better results than vdw-DF in the case of graphite. About CP, some time ago I interfaced the DFT-D2 module of PWscf to cp.x. At that time, I used the 4.2 release of espresso, which is a little old now. I can send you that old package if you are interested. We also tested the DFT-D3 method on a couple of systems and, in my opinion, it does not give very exciting results. But interestingly, as suggested by Giuseppe, in some cases we found a good agreement between DFT-D3 and vdw-DF data. Hopefully the two series vdw-DF(n) and DFT-D(n+1) will converge to the same result :)
regards daniel 2011/3/23 Gabriele Sclauzero <sclauzer at sissa.it> > Dear Giuseppe, > > I think your reply reached also the PW-forum, since I've received it > twice, so everyone should have been able to read it. > > Il giorno 23/mar/2011, alle ore 10.48, giuseppe.mattioli at mlib.ism.cnr.itha > scritto: > > Dear Gabriele > > is there any concrete evidence that "ab initio" van der Waals > > vdW-DF is systematically better than Grimme's vdW? > > > Yes, at least in the case of molecule-surface interactions. > > > Maybe graphite is another story... with PBE-D2 you should get an interlayer > spacing just 3.4% smaller than the experimental value, which is not so bad > considering the much larger PBE error. > > > There is a > recent (2010) Grimme paper (I'm sorry, I cannot be more accurate > today...) > > > Maybe this one: > THE JOURNAL OF CHEMICAL PHYSICS *132*, 154104 (2010) > which is the paper introducing the D3 method (and a comparison with its > predecessor D2) > > that reports an overestimate of the above interactions when > using DFT-D2, currently implemented in QE. I've performed comparative > tests (classical MM, DFT-D2, vdW-DF) on several molecules interacting > with the non-polar 10-10 ZnO surface and I've obtained the best > results (some of them comparable with experimental data, i.e., the > thiophene ring) by using the vdW-DF approach. The DFT-D2 setup, > however, is quite good for molecules in my experience, and can be > tuned by changing the C6 coefficients by hand > (QE/Modules/mm_dispersion.f90), following one of the available force > fields (AMBER, CHARMM, ...). > > Maybe DFT-D3 and vdW-DF would converge to > similar results... > > > I can't tell this, but I know that DFT-D3 should include some notable > improvements with respect to the D2 version, since it now takes into account > some kind of local coordination of the atoms, atom-pair specific > coefficients (from ab initio), and should also separate better the long > range regime from the short range one. I know there is someone who offered > to look at implementing the extension to D3, maybe it will be available in a > few months time. > > What about cp? > > > No clear idea here. However I believe it should not be difficult to port > DFT-D2 to CP, since it requires only atomic positions and the cell setup. > These should be handled in a similar way in PW and CP. > > > Gabriele > > > Yours > > G. > > Quoting Gabriele Sclauzero <sclauzer at sissa.it>: > > Dear Giuseppe, > > > is there any concrete evidence that "ab initio" van der Waals > > vdW-DF is systematically better than Grimme's vdW? > > Are you aware of any paper comparing the latest version of the two > > methodologies (or "phisolophies", if you want), i.e. vdW-DF2 vs > > DFT-D3? > > > Cheers, > > > GS > > > > Il giorno 23/mar/2011, alle ore 10.12, > > giuseppe.mattioli at mlib.ism.cnr.it ha scritto: > > > > Dear all > > You can do better than the semiempirical "Grimme" correction. There is > > a new ab initio van der Waals correlation functional implemented in QE > > 4.3a. Try input_dft='vdW-DF', in the &sysytem list. > > By the way, what about a (semiempirical or ab initio) vdW scheme in > > cp.x? Is there any project going on? > > > Yours > > > Giuseppe > > > Quoting Masoud Nahali <masoudnahali at gmail.com>: > > > Dear Eric > > > Try london="true" to get improved answer; as you should know DFT is weak > > to calculate dispersion forces and by using the keyword one can include > > these forces semi-empirically. I hope it helps. > > > Best Wishes > > > Masoud > > -------------- > > Masoud Nahali, Sharif University of Technology > > > > Eric Wrote: > > > Dear all, > > > I'm trying to optimize unit cell parameter of graphite. > > The problem is the c axis gets too long. > > Starting from published data my initial parameters are a=4.59203 Bohr > > and c=12.513 Bohr. > > The final values are 4.664 and 15.829 respectively. > > I need someone to explain to me what I did wrong, I've attached my input > > file. > > That's a basic calculation so it's very frustrating to not make it done. > > I thank you in advance, > > > Eric. > > > -- > > /Be the change you wish to see in the world > > / --- Mahatma Gandhi --- > > > Dr. ?ric Germaneau <mailto:germaneau at gucas.ac.cn > > <http://www.democritos.it/mailman/listinfo/pw_forum>> > > > College of Physical Sciences > > Graduate University of Chinese Academy of Sciences > > Yuquan Road 19A > > Beijing 100049 > > China > > > > Giuseppe Mattioli > > ISM-CNR > > Italy > > > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://www.democritos.it/mailman/listinfo/pw_forum > > > > ? Gabriele Sclauzero, EPFL SB ITP CSEA > > PH H2 462, Station 3, CH-1015 Lausanne > > > > > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > > > ? Gabriele Sclauzero, EPFL SB ITP CSEA > * PH H2 462, Station 3, CH-1015 Lausanne* > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -- ---------------------------------- Daniel Forrer Dipartimento di Scienze Chimiche Universit? degli Studi di Padova V. Marzolo 1, Padova mail daniel.forrer at unipd.it tel. +39 049 8275166 ---------------------------------- -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110323/b931d5d5/attachment-0001.htm
