[DFTB-Plus-User] Dear DFTB plus users. I am trying to construct the SK parameter file by myself. But i can understand some part.

[Peter Yen]

Dear Mr. Bálint :
Your suggestions are much appreciated. I now can successfully convert the
 SK parameter from HOTBIT to the one which DFTB+ can recognize. The energy
( band,coulomb and repulsive) are almost identical, with just slightly
differences. Although i think Pekka's parameter set is a little
oversimplified since he only fitted to gold dimer, but i think it is a
start for parameterization works for gold in DFTB+ program. I am really
grateful to your assistance.


                                                              With Best
Regards
                                                               Peter


2014-11-13 0:03 GMT+08:00 Bálint Aradi <aradi at uni-bremen.de>:

> Dear Peter,
>
> > 1.  Line 1  gridDist nGrdPoints
> >      What is the unit for gridDist?  Is it angstrom or atomic unit?
>
> Everything always atomic units (Bohr radius) unless explicitely declared
> being something else.
>
> >
> > 2. Line 4~4+nGridpoints-1:
> >     The document mentions that in  this block , the distance will be
> > increased one "gridDist" unit between each line. I would like to ask is
> > the distance for line4 refering to "0" ? Or does it  refering to R_0?
>
> It corresponds to the distance dr, where dr is the step between the grid
> points. The documentation uses the symbol r0, but this has nothing to do
> with the compression radius r0.
>
> You can test it by setting up an H2 molecule with a distance between the
> atoms being equal to one of the tabulated grid points and setting
> WriteHS=Yes, which would print your H and S matrices. You should see the
> same elements as in the SK-table.
>
> > 3.Spline block
> >    line4 to 4+nInt-2, what is the unit for nInt? Is it angstrom or
> > atomic unit?
>
> See comment 1.
>
> >
> > 4. This is the some part extracted from from mio-1-1/C-C.skf
> >
>    i dont understand from line4 to line22, can someone explain to me? I
> > thought it was the H and S matrix elements but it seems not because the
> > total nGridpoints is 500 ( from line 23 to line 522) and it seems the
> > block of H and S matrix elements don't include line4 to line22. Can
> > anyone tell me the purpose of line 3 to line22 ?
>
> For historical reasons, integrals were not generated for distances below
> 0.4 au. Corresponding values are filled up with some arbitrary values,
> usually zeros. Note, that in the DFTB, results for atoms getting closer
> than 0.4 au are questionable anyway.
>
>   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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>


-- 
Research Assistant,Physics
Department,NCU,Taiwan
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