[Pw_forum] Lattice constants with vdW-DF/vdW-DF2

[Duy Le]

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
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