[Pw_forum] Phonons with DFPT and DF2 functional

[Florian Altvater]

Hi Paolo,
thanks for the info. A check would definitely be helpful as long as it
is not implemented.

Thanks,
Flo


Am 05.11.2014 um 11:06 schrieb Paolo Giannozzi:
> On Wed, 2014-11-05 at 03:51 -0800, 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?
> DFPT + vdW (any kind) is not currently implemented. The next version
> (out in a few days) will contain a check on this
>
> Paolo
>
>> 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
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