[DFTB-Plus-User] Any chance to mimic by DFBT+ the results of hybrid functional (B3LYP. PBE0) ?

[Bálint Aradi]

Dear Michal,

I think, it depends, whether the effect is due to the functional choice 
(being PBE in most DFTB parameterizations) or due to the fitted 
repulsive potentials.

If it is mainly a functional problem, one usually should not to try to 
fix it by changing the fitted repulsive potentials, as this might have a 
bad influence on transferability. One should rather use the correct 
functional within DFTB as well. DFTB+ offers long range corrected 
(hybrid) functionals for molecular systems already. The extension to 
periodic systems is on the way (a first implementation is already being 
tested), so it should soon become part of the official DFTB+ version.

If it is not a problem with the chosen functional, then refitting the 
repulsive potentials might be helpful, indeed. As Jan pointed out, there 
had been efforts into that direction already several years ago. In a 
more recent approach, three-body potentials using the ChIMES force field 
were used very succesfuly as well. DFTB+ can already read ChIMES force 
field data to correct the repulsive potentials, and now also the fitting 
framework is publicly available:

https://github.com/rk-lindsey/chimes_lsq

We unfortunately miss a detailed tutorial for this parameterization 
tool-chain so far, but I have some promises from the authors, that this 
will be soon delivered (let's hope on New Year's resolutions :-D).

Best regards,

Bálint



On 28.12.22 08:51, Husak Michal via DFTB-Plus-User wrote:
> Hi
> 
> 
> I need to observe by molecular dynamic jumping on H atom between O and N in molecular crystals.
> 
> The effect is visible during molecular dynamic runs (when I use meta-GGA or hybrid functionals) .
> 
> DBFT+ molecular dynamic run doe snot see the effect - it makes the O-H bond breaking impossible .
> 
> 
> Is there any way to calibrate DFBT+ for given system to be able to reproduce rSCAN or PBE0 results ?
> 
> 
> The key reason of this effort - the molecular dynamic calculation by the rSCAN/PBE0 are extremely computation expensive so we can not make them for enough big systems ...
> 
> We even must do PIMD to include NQE effect = 16x more power require ...
> 
> 
> Michal Husak
> 
> UCT Prague
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-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b-aradi/


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