[DFTB-Plus-User] DFTB xTB-GFN2

[Bálint Aradi]

Dear James,

thanks a lot for the feedback on GFN2-xTB. As the feature is very new 
and under heavy development, there may be still bugs there. We really 
appreciate your feedback on it, as it helps us to identify the remaining 
issues.

Would you mind to create a formal issue (maybe with the input you used) 
on GitHub? It would be much easier for us to keep track of it and to 
ensure, that it gets fixed before the next DFTB+ release.

Best regards,

Bálint

Ps. If anybody else is interested in **testing** the GFN2-xTB 
implementation in the development version of DFTB+, you should download 
the source from the main branch on GitHub and compile it yourself. 
Feedbacks, bug reports (preferably on GitHub) are very welcome. But 
please note, that GFN2-xTB in DFTB+ is not considered yet as 100% 
stable, so do not use it in production runs yet.


On 16.07.21 16:32, James A Charles wrote:
> Hi,
> 
> I recently saw that you were adding the GFN2 tight binding model to 
> DFTB+ and was quite excited to try it. I did some basic tests with water 
> dimers and trimers and got strange results. Perhaps there is a bug?
> 
> Here is for the dimer but similar for the trimer, GFN2 gives a negative, 
> unphysical, binding energy :
> 
> model
> 
> 	
> 
> Calc. binding energy [kcal/mol]
> 
> 	
> 
> Ref. binding energy* [kcal/mol]
> 
> 	
> 
> Relative diff. %
> 
> mio
> 
> 	
> 
> 4.99247
> 
> 	
> 
> 4.99
> 
> 	
> 
> 0.05
> 
> 3ob3-1
> 
> 	
> 
> 4.59272
> 
> 	
> 
> 4.99
> 
> 	
> 
> -7.96
> 
> GFN1
> 
> 	
> 
> 4.80922
> 
> 	
> 
> 4.99
> 
> 	
> 
> -3.62
> 
> GFN2
> 
> 	
> 
> -53.46331
> 
> 	
> 
> 4.99
> 
> 	
> 
> -1171
> 
> 
> *J. Phys. Chem. B 2005, 109, 33, 15677–15683
> 
> 
> Is there anything I'm missing?
> 
> James Charles, PhD
> Senior Research Associate
> School of Electrical and Computer Engineering
> Purdue University
> 465 Northwestern Ave,
> West Lafayette, IN 47907
> 
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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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