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

[Karol Strutynski]

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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