[DFTB-Plus-User] Possible bug, stress tensor and vibrational modes

Bálint Aradi balint.aradi at bccms.uni-bremen.de
Fri Apr 30 08:02:21 CEST 2010


Dear Hegoi Manzano,

> I will repeat a previous email without answer, just in case, adding this time a new question. I have started using the new dftb+ 1.1 release, and I found some problems.

 Not sure, which email you refer to, as the last one of yours arriving
on the list was actually answered. See

http://www.dftb-plus.info/pipermail/dftb-plus-user/2010/000458.html

and the follow-up. Or was there anything else escaping our mailing list
archive?

> 2.- I have some slako files with a polynomial representation of the repulsion instead a spline. With the previous release they work (the snapshot) they work, but now I get the error:
> 
> ERROR!
> -> Incompatible repulsive polynomial coefficients  for the species pair  1- 2

 We introduced a strict compatibility check for the SK-files in the new
version for various reasons. The error above means, that the polynomial
repulsive coefficients for type 1 and 2 (Si and O I guess in your case)
differ in the two heteronuclear files (Si-O vs. O-Si), which actually
should not be the case, as it does not make much sense. Could you please
check on this? If the polynomial coefficients are the same, could you
just send me the SK-files so that I can check, why does the code issue
the false alarm.

> 3.- How can I calculate the vibrational modes for a given small cluster?

 Calculate the Hessian via the appropriate Driver setting, and then use
the modes code to diagonalize it and get the frequencies and the normal
modes.

  Best regards

   Bálint


-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/en/~b_aradi


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