[DFTB-Plus-User] Number of external charges in DFTB+

Benjamin Woiczikowski p.woiczikowski at tu-bs.de
Wed Feb 11 17:01:14 CET 2009

Dear Bálint,

thanks a lot for the help, it works now by setting the maximal stack size to 

The read-in of external charges is very slow compared to the old dftb. Is that 
because we are using Intel compiler? Is there any chance to make this faster?

Best regards,


Am Mittwoch 11 Februar 2009 04:27:53 schrieb Bálint Aradi:
> Dear Ben,
> > I want to calculate a molecular system in presence of an electrostatic
> > field. The electrostatic field consists of more than 20,000 atoms and
> > when I run DFTB+ there is an segemtation fault.
> >
> > I think there has to be a limit for external charges, since it works
> > perfectly with only a few external charges.
>   Theoretically (!) there is no limit for the number of external
> charges. Practically, there could be one, especially if using the Intel
> compiler for compilation:
>   If some arithmetic expression in the code uses the matrix of the
> charges, then a temporary product is created during evaluation. If it
> exceeds the stack size (which is per default 8 MB in bash/tcsh), then a
> segmentation fault occurs in the ifort compiled binaries. Could you try
> to set the maximal stack size in your shell to unlimited and try it again?
>   bash: ulimit -s unlimited
>   tcsh: limit stacksize unlimited
> Please check if those settings solve the problem. Should it be not the
> case, please just send me your input (including geometry and SK-files)
> as a tgz archive, so that I can try to reproduce the case.
>   Best regards,
>     Bálint
> Ps. I carbon copied your email to the DFTB+ User list. Please in the
> future post questions regarding the use of DFTB+ to that list, so that
> also other people can profit from the discussion.


Paul Benjamin Woiczikowski
Department of Physical and Theoretical Chemistry
Technische Universität Braunschweig
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