It is well-known that vdW-DF and vdW-DF2 overestimate lattice parameters of solids See this work: Phys. Rev. B 83, 195131 (2011) -------------------------------------------------- Duy Le PhD Candidate Department of Physics University of Central Florida.
"Men don't need hand to do things" On Thu, Sep 1, 2011 at 3:27 PM, Ari P Seitsonen <Ari.P.Seitsonen at iki.fi> wrote: > > Dear Colleagues, > > ?I want to calculate molecules adsorbing on metallic surfaces, and since the > adsorption energy of them is know to be small, I would like to apply the > vdW-DF/vdW-DF2 for the calculations. When I calculate the lattice constant > with those functionals, I seem to get very large lattice constants, 5-10 % > larger than the experimental one. An example for bulk, fcc gold is attached. > I perform the calculation looping over different values for the lattice > constant; the result seems to be independent of the cut-off energies (in > this case I have large values for 'ecutwfc'/'ecutrho' because this was the > last run for the convergence tests). > > ?Thus my question, does any one see something wrong in my input? Since the > exchage part of the exchange and correlation is treated with a GGA > functional (independently whether I use vdW-DF2 and PW86 or vdW-DF and > revPBE) and correlation with LDA, plus an attractive(?) long-range > contribution, I would expect lattice constants much closer to the > experiments. > > ? ?Greetings from Wroclaw, > > ? ? ? apsi > > PS Apologies if the topic of my mail is an FAQ/discussed already! > > -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- > ?Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/ > ?Physikalisch-Chemisches Institut der Universitaet Zuerich > ?Tel: +41 44 63 54 497 ?/ ?Mobile: +41 79 71 90 935 > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > >
