[DFTB-Plus-User] R: UV-Vis Calculations and in error (NrOfExcitations)

[Thomas Niehaus]

Dear Daniele,

when you say the system was well optimized, did you check the state 
occupations at the final structure (-> band.out)? Is your system 
zwitterionic, are the ligands maybe charged....

Did you run the tutorial with the geometry and input file for that 
tutorial? I don't understand what you mean with relative geometry.

Best Thomas


On 2/15/23 5:03 PM, daniele.veclani at isof.cnr.it wrote:
>
> Dear Thomas,
>
> first of all thanks for your reply, no my system is a protein fragment 
> + ligand, and this system was well optimized before the UV-vis 
> calculation.I don't understand where the metallic character can come 
> from. However I get the same error even if I run the tutorial input 
> (with relative geometry) found in the DTFB+ recipes 
> (recipes_DFTB+/linresp/macromolecule).
>
> And I don't understand why also the tutorial calculation crashes.
>
> Do you have any suggestion?
>
> Best regards,
>
> Daniele.
>
> *Da:*DFTB-Plus-User <dftb-plus-user-bounces at mailman.zfn.uni-bremen.de> 
> *Per conto di *Thomas Niehaus
> *Inviato:* mercoledì 15 febbraio 2023 16:56
> *A:* dftb-plus-user at mailman.zfn.uni-bremen.de
> *Oggetto:* Re: [DFTB-Plus-User] UV-Vis Calculations and in error 
> (NrOfExcitations)
>
> Dear Daniele,
>
> it seems that your system is metallic. There are several fractional 
> occupations. This means that the response matrix to diagonalize 
> becomes gigantic and that there are clusters of near zero excitation 
> energies which the iterative eigensolver can not separate.
>
> I would suggest to identify the origin of the metallic behaviour. Is 
> the structure chemically sound?
>
> Best regards
>
> Thomas
>
>   
>
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-- 
Prof. Dr. Thomas Niehaus
Institut Lumière Matière
UMR5306 CNRS
Université Claude Bernard Lyon 1
Domaine Scientifique de La Doua
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--
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