[DFTB-Plus-User] Running the code successfully and several problems

[Bálint Aradi]

Dear Xiaobao Zhang,

> *But it is RelativelyRobust{}, the program refuses to run.  There are
> 288 carbon atoms in my system. *

RelativelyRobust is not implemented, as it only got part of ScaLAPACK
since version 2.0. We will add a binding to it in the near future.

> *2) The bigger for the EwaldParameter, the longer for the  computer time.*
>       EwaldParameter = 0.0,   time=3 minutes;

The Ewald parameter changes whether more summation is done in real or
reiciprocal space. Small Ewald parameter means more real space
summation, which is usually more fortunate. However, it can increase
your neigbhor list length significantly. At some points, it can even
become a memory bottleneck.

> I find the bigger for the RowBlockSize and ColBlockSize, the longer for
> the  computer time.
> I want to know whether I should set the RowBlockSize and ColBlockSize 
> smaller as soon as possible for any system?  Or only set them the
> default values.

Hard to say, it is the block size BLACS (ScaLAPACK) uses. Try various
values and see it for yourself. For our system and my problems, 32 was
optimal.

>  I set the Group=1 and 2 when I use the kpoints, there are no different
> phenomenon for the results, including the computer time.

Depends again on how many k-point you have, how big your system size is.
It should give some speedup if your system size is rather small and you
have many k-point and spin degree of freedom.

  Best regards,

    Bálint

-- 
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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