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

[Emine Kucukbenli]

Dear Ari,
I see in Modules/funct.f90 that
'VDW-DF2-C09' sets this configuration:
SLA+PW+Cooper 09+vdW-DF2

'VDW-DF-C09' instead:
SLA+PW+Cooper 09+vdW-DF

Cooper 09 (c09x) is the new grad.x i mentioned.
While generating the pseudopotentials, as long as you keep grad.  
exchange as c09x, the grad.correlation should not matter as it is  
overwritten by the vdWDF/DF2.
best,
emine


Quoting Ari P Seitsonen <Ari.P.Seitsonen at iki.fi>:

>
> Dear Emine,
>
>   Thank you very much - I _was_ able to see your emails on the mailing
> list. I'll have a look on these alternative exchange functionals - do
> you mind telling me what is the syntax for them in the input for Q-E?
> And which pseudo potentials (which XC) do you employ with it?
>
>     Thank your again,
>
>        apsi
>
> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
>   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
>
>
> On Thu, 1 Sep 2011, Emine Kucukbenli wrote:
>
>> Hi Ari,
>> (I dont see my mail delivered so I am writing again, sorry if   
>> anyone receives it twice)
>> You can try c09x exchange functional which is claimed to solve that issue:
>>
>> V. R. Cooper, Phys. Rev. B 81, 161104(R) (2010)
>> It is recently implemented in QE.
>> best,
>> emine kucukbenli, phd student, sissa, italy
>>
>> Quoting Ari P Seitsonen <Ari.P.Seitsonen at iki.fi>:
>>
>>>
>>> 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).
>>>
>>
>>
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