[DFTB-Plus-User] Why the Borg-0-1 parameter set gives a negative repulsive potential value?

[Peter Yen]

Dear Daniel:
The reference "SCC-DFTB parameterization for boron and boranes. J. Chem.
Theory Comput. 8, p. 1153" states that the parameter set is applicable to
finite and perodic systems. I assume that this means it can be used for
boron clusters. Also in dftb website they claim that this parameter set is
fitted to molecular system so i think it should work even better for boron
cluster. Anyhow, it shouldn't generate a negative value for "repulsive "
energy. Forget to mention, my system is B_20 and the input structure is
obtained from a global optimization program.


       Best

       Yen


2014-03-19 11:31 GMT+08:00 Daniel Massote <dmassote at yahoo.com>:

>  Dear Yen,
>
> I think this set is not fitted for clusters, but for surfaces and
> nanotubes. Check the description inside the file.
>
> Daniel Massote
>
> Em 03/18/2014 10:40 PM, Peter Yen escreveu:
>
> Dear DFTB users
> I am recently calculating the boron cluster using the updated Borg-0-1
> set.
> this is what i obtained
>
>   Energy H0:                      -18.7377446328 H     -509.879974 eV
>  Energy SCC:                       0.0191313122 H        0.520589 eV
>  Total Electronic energy:        -18.7186133206 H     -509.359384 eV
>  Repulsive energy:                -3.0082889554 H      -81.859707 eV
>  Total energy:                   -21.7269022760 H     -591.219092 eV
>  Total Mermin free energy:       -21.7269107158 H     -591.219321 eV
>
>  As you can see the repulsive energy is "negative".  This doesn't happens
> when using the mastsc-0-3 set for Boron. Is anything wrong with the
> parameters. I think that repulsive energy is negative is unphyiscal, right?
>
>
>
>
>        Best
>
>      Yen
>
>  --
> Research Assistant,Physics
> Department,NCU,Taiwan
>
>
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-- 
Research Assistant,Physics
Department,NCU,Taiwan
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