[DFTB-Plus-User] Can 3ob SKF files be used for non-SCC calculations?

[SRKC Sharma Yamijala]

Dear all,

I have been trying to optimize Graphene Quantum dots with/without
passivating them hydrogen atoms. Usually, I am getting the "SCC is NOT
converged" error. Error is many a times with non-passivated GQDs, but, it
is not so uncommon in passivated GQDs either.

I have tried the below things, but, I was not successful.

1. I have reduced the SCC tolerance to 10^-4
2. Increased the no.of SCC iterations to 1000
3. I have changed the Fermi temperature. (Though this one gave me the
converged geometries, these geometries are looking like amorphous carbon
rather than any possessing any lattice structure/ molecule structure. I got
this spurious structures even with 1K temperature).

Finally, I would like to give a try with the non-SCC calculations. But,
before that, I would like to know whether I can use 3ob SKF files for the
calculations or there any other specific SKF files. (I will obviously
remove DFTB3 and SCC related parts in the input file).

Also, I will be really happy to know, if there are any other suggestions to
get converged geometries with DFTB3.

Thanking you for your support,
Sincerely,
Sharma.

P. S:
To reproduce the errors I am providing the input files of non-passivated
and passivated GQDs (prefixed with PAH_) GQDs along with the SKF files. I
have used 3ob parameters.



********************************************************
*Chaitanya Sharma,*
*Prof. Pati'*s group,
Chemistry and Physics Materials unit,
JNCASR, BANGLORE,
Lab:: (080-2208) 2581, 2809
https://sites.google.com/site/sharmasrkcyamijala/
*********************************************************
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