[DFTB-Plus-User] Geometry is way off while using DFTD3...

[siddheshwar chopra]

Dear Karol,
Thank you for the information. I used the DFTD3, Grimme's correction. I had
dftb optimization result, and then ran again separately with dftd3{}. I ran
scc with dftd3.
Please could you throw more light into this?

Regards,

On Mon 7 May, 2018 4:47 pm Karol Strutynski, <strutynski.karol at gmail.com>
wrote:

> Hello,
>
> I encountered similar problems myself, but as it turns out it was my error:
> You have to be sure that you check the right minima with right hamiltonian.
> Practically speaking, the given structure is minima only with Hamiltonian
> you used to get it.
> You have to ensure that you have third order terms in your frequency
> calculations for checking DFTB3 minima.
>
> Best Regards,
> --
> Karol Strutynski
> CICECO - Aveiro Institute of Materials
> Department of Chemistry
> Universidade de Aveiro
> Office 29.3.25
> 3810-193, Aveiro, PORTUGAL
> Phone: +48 739259476
> Mail: strutynski.karol at gmail.com, skarol at ua.pt
> ORCID: http://orcid.org/0000-0001-8733-9012
>
> On Mon, 7 May 2018 at 12:11, siddheshwar chopra <sidhusai at gmail.com>
> wrote:
>
> > Dear Balint,
> > I am trying to compare DFTB and DFTD3 ground state optimization results.
> > I find that total energy obtained in DFTD3 is -2.7300 eV more than the
> DFTB energy. That seems good to me. But, when I am checking for negative
> frequencies, I find the geometries to be way off....
>
> > For DFTB:
> >      1   -2.47
> >      2   -1.34
> >      3   -0.53
> >      4   -0.35
> >      5    0.54
> >      6    1.42
>
> > For DFTD3:
> >     1  -83.05
> >      2  -32.67
> >      3  -24.61
> >      4    9.71
> >      5   26.44
> >      6   39.63
>
> > Please tell me how to understand this and how should I proceed?
>
> > Regards,
> > --
> > Dr. Siddheshwar chopra,
> > M.Sc., Ph.D (Physics)
> > Assistant Professor (Physics),
> > Amity University, Noida, India.
>
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