[DFTB-Plus-User] Query on the use of DFTB+ for solid state calculations

[Bálint Aradi]

Dear Bhuvaneswari R,

yes, you use the right parameter set. You should take into account, that 
minimal basis methods (DFTB, xTB) usually use strongly compressed atomic 
orbitals as basis in order to describe intramolecular chemical bonds 
correctly. As a consequence, the intermolecular interactions might be 
less precise, as the basis functions decay too fast outside of the 
molecule. Therefore, depending on your system, the 2% limit might be too 
high.

Best regards,

Bálint



On 01.03.23 16:12, Bhuvaneswari Ramaganesan wrote:
> Greetings,
> 
> This is Bhuvaneswari R, Ph. D student at JNCASR, India. I am currently 
> using DFTB+ to optimize a molecule (hexachlorobenzene) so that I can 
> create a molecular crystal out of it. In order to optimize the molecule, 
> I used the default dispersion parameters of DFTD3 and Slater Koster 
> files (3ob) from DFTB. The error in lattice constants after optimization 
> is greater than 2 %.
> 
> Am I using the right Slater-Koster files? Is there any modified file for 
> solid-state calculations? To achieve accurate optimization (within error 
> bar limit), how can the dispersion parameters be tuned? Can you please 
> help in choosing the right parameters? Thank you.
> 
> Regards,
> Bhuvaneswari R
> 
> 
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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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