dispersion interactions, aka vdW, are not included in LAD/GGA/Hybrid functionals
this is why DFT-D (switched on by the "london=.true." keyword) introduces an empirical damp-dispersion term interaction between permanent dipoles and the one between permanent charges/dipoles and statically induced dipoles is just electrostatic and is therefore correctly included in the Hartree term. Notice that there are new generation of fully non local XC functionals vdW-DF, vdW-DF2 and soon VV10 (or actually a refinement of it) that are implemented in QE. Check the beginning of Modules/funct.f90 for a list of options and some relevant references. As these functionals are not implemented in the ld1.x code one needs to force their use by the input_dft keyword.. and chose some reasonable, not too different, xc functional for the pseudopotentials. hope this helps stefano Quoting manoj narayanan <manojnarayan86 at gmail.com>: > Dear Masoud > Thank you for your reply, but what my doubt is > that QE only includes london dispersion. What about other effects like > Keesom and Debye forces ? > > Yours Sincerely > Manoj > > On Sun, Aug 12, 2012 at 4:11 PM, Masoud <masoudnahali at gmail.com> wrote: > >> >> Dear Manjo >> >> QE can calculate semi-empirical dispersion term, setting "london=.true." >> you can include such interaction which is weakly calculated by pure DFT in >> your calculations. I hope it helps. >> For details please see >> >> S. Grimme, J. Comp. Chem. 27, 1787 (2006), and >> V. Barone et al., J. Comp. Chem. 30, 934 (2009) >> >> >> >> >> Best Wishes, m >> >> >> >> >> >> ---------------------------------------- >> Masoud Nahali >> SUT >> masoud.nahali at gmail.com >> alum.sharif.edu/~m_nahali >> >> >> >> >> >> On Sun, Aug 12, 2012 at 9:37 AM, Manoj wrote: >> >>> >>> >>> Dear users >>> In my calculation with carbon chain between >>> 9 >>> to 12 carbon atoms I have to include Van der walls interaction and I am >>> not >>> clear about it's inclusion in DFT. What all are the key words >>> and parameters for that and how effective is the implementation? Can >>> anyone shed some light in to this. >>> >>> Thanking all in advance >>> Manoj >>> -------------- next part -------------- >>> An HTML attachment was scrubbed... >>> URL: >>> http://www.democritos.it/pipermail/pw_forum/attachments/20120812/91b1104f/attachment.html >>> >>> >>> >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum >> >>