[Pw_forum] Phonons with DFPT and DF2 functional

[stefano de gironcoli]

Dear Florian Altvater
     the calculation of vibrational properties with vdw-DF functionals 
is not yet in the public version.
     it should be released soon.

Stefano de Gironcoli
SISSA and DEMOCRITOS


On 11/05/2014 12:51 PM, Florian Altvater wrote:
> Hi,
> I am interested in looking at effects of using van der Waals functionals
> like vdW-DF2 on the phonon dispersion of organic crystals. Preliminary
> results indicate that there might be some issues with using DFPT and DF2
> together. More specifically, DFPT gives a couple "very imaginary"
> frequencies (below -100cm^-1) for Gamma-point phonons (with and without
> acoustic sum rule), while finite displacement results seem to be just
> fine, using the same convergence parameters.
>
> So before I dig deeper into eventual other issues at play here, I wanted
> to ask if you know of any incompatibilities when using DFPT and vdW-DF2?
> Either inherently embedded in the underlying theory (which I could then
> dig into first), or just in the way it is implemented in QE.
>
> Thanks for your help,
> Florian
>
> ---
> Florian Altvater
> PhD candidate
> UC Berkeley/LBNL
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum