[DFTB-Plus-User] Format of skf files

Ben Hourahine benjamin.hourahine at strath.ac.uk
Wed Sep 2 18:25:15 CEST 2009

Hello Carlos,

These are values for inter-atomic separations very close to the atomic
core region, typically within 0.2 Angstroms, and well inside the
region that the repulsive interaction is of exponential form. In a real
simulation inter-atomic distances in this range are not going to
actually occur, and if they did there will be substantial repulsive
forces pushing the atoms apart.

The 20*1.0 format is a quirk of the fortran language, so as you say, in
this region the hamiltonian and overlap elements are (artificially) set
to 1, and then the table jumps to actual values beyond this region.

Historically I think the reason for this was that some of the numerical
integrals becomes more difficult for the rapidly oscillating single
particle wavefunctions in this region, so was cut off.



Carlos Reis wrote:
> Dear Bálint
> Some skf parameter files have lines like the following after the 3rd
> (in the homonuclear case) while others do not:
> 20*1.0
> 20*1.0
> 20*1.0
> 20*1.0
> 20*1.0
> 20*1.0
> 20*1.0
> 20*1.0
> 20*1.0
> Does this means that the Hamiltonian and Overlap matrix elements start
> at 1.0 and then "jump" discontinuously  to other values? I'm a bit
> puzzled about this.
> Any help will be greatly appreciated.
> Best regards, Carlos Reis.
> _______________________________________________
> DFTB-Plus-User mailing list
> DFTB-Plus-User at dftb-plus.info
> http://www.dftb-plus.info/mailman/listinfo/dftb-plus-user

     Dr. B. Hourahine, SUPA, Department of Physics,
   University of Strathclyde, John Anderson Building,
          107 Rottenrow, Glasgow G4 0NG, UK.
    +44 141 548 2325, benjamin.hourahine at strath.ac.uk
   The University of Strathclyde is a charitable body,
registered in Scotland, with registration number SC015263

More information about the DFTB-Plus-User mailing list