[QE-users] Convergence wrt. to cutoff: VdW vs. no VdW correction

[Fabrizio Cossu]

   Dear Chris and Paolo,
I experienced slightly different behaviour between the inclusion or not of
vdw-d. I'm using QE 6.3, on a layered material with vdW bondings between
layers. I would think such behaviour is normal, as vdW corrections modify
the distance between layers, hence the expansion of the plane waves. In
particular, for a molecule in a box convergence wrt energy cutoff can be
even less straightforward.

   Cheers,
   Fabrizio

On Wed, 15 May 2019 at 17:08, Paolo Giannozzi <p.giannozzi at gmail.com> wrote:

> Very strange: as far as I remember. dft-d3 does not depend upon the cutoff
>
> Paolo
>
> On Wed, May 15, 2019 at 2:48 AM Christoph Wolf <wolf.christoph at qns.science>
> wrote:
>
>> Dear all,
>>
>> I noticed something interesting: when testing the convergence of total
>> energy wrt. ecutwfc (keeping ecutrho at 4*ecutwfc and using NC PPs) the
>> convergence without vdW is fairly straightforward and monotonous, however
>> with grimme-d3 VdW correction applied the behavior of total energy becomes
>> very "jumpy", it has plateaus between certain values of the ecutwfc but
>> then jumps and is generally very hard to converge - any hints on how to
>> improve that for calculations of "molecules in a box"?
>>
>> Thanks in advance for your help!
>>
>> Best,
>> Chris
>>
>> --
>> Postdoctoral Researcher
>> Center for Quantum Nanoscience, Institute for Basic Science
>> Ewha Womans University, Seoul, South Korea
>>
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>
>
>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
> _______________________________________________
> Quantum Espresso is supported by MaX (www.max-centre.eu/quantum-espresso)
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-- 

*Fabrizio Cossupostdoctoral fellow at APCTP (Asia Pacific Center for
Theoretical Physics)*,
Hogil Kim Memorial Building #501
POSTECH, 67 Cheongam-Ro, Nam-Gu,
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790-784 (37673), Republic of Korea
*Telephones:*
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