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. There is a recent (2010) Grimme paper (I'm sorry, I cannot be more accurate today...) 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... What about cp? 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 > >
