[Pw_forum] How to use vdW-df in QE?

[Saif Ullah]

Dear Paolo/Karim,

Thank you very much for your prompt response. Actually, you missed the
first part of my question. Can we use PBE pps by just changing the
input_dft? Of course, the generate_vdw_kernel_table should be present. We
use VDW-DF-SIESTA and M06 etc in Gaussian and sometimes we also use VASP.
Our generated vdW-DF-SIESTA pps give the same results as that of Gaussian
and VASP. SOmedays ago, I posted a problem regarding the bad energetics of
graphene+Li. One of the QE developers asks me to calculate different
systems with the different level of theories. The binding energy for
Li+graphene is found to be overestimated using QE, while for Na the results
were pretty much comparable. I also calculated vdW-DF (optb88-vdW) using
PBE pps in QE and luckily the binding energy was the same as calculated by
optpbe-vdW using VASP. I'm interested to use different pps and different
level of theories using QE and compare with the other codes. Therefore, I
came up with this question. Learning PPs generation needs lots of time as I
already spent much time in learning for SIESTA.

Dear Karim,

Thank you very much. That's why I came up with this question as by using
optb88-vdW with PBE pps gave me the same results of Na binding on graphene
as of optpbe-vdW using VASP.

Let's see what experts say.

Thanks

Saif
Department of Physics, UFJF, Brazil

On Tue, Oct 24, 2017 at 12:06 PM, Karim Elgammal <egkarim at gmail.com> wrote:

> Hi Saif;
> to the extend of my limited experience; yes, you can use by changing the
> input_dft and ofcourse generating the vdW kernel using generate_vdW_kernel_table.x
> before you start your calculation..
>
> input_dft: will override the functional definition in your input PPs...
>
> note: wait also for opinions from experts here, I am just sharing my
> experience.
>
> Karim Elgammal
> KTH
> Sweden
>
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