electron density cube file after DFTB

[Bálint Aradi]

Hi,

> in the tight-binding method the basis functions are not
> explicitely defined. The definition is implicit in the
> overlap and energy integrals.
> Therefore there is no way to calculate the electron density
> on a grid for these methods.

That's not 100%-ly precise that way. When you generate the Hamiltonian
and overlap integrals for DFTB, you use a certain basis with well
defined basis functions. If you keep those basis functions, you can
construct your molecular orbitals and your density based on those
functions and on the eigenvectors spit out by the DFTB method.

  We use the tool Waveplot for doing that [1]. Unfortunately it only
works with DFTB+, but it shouldn't be very complicated to create a
similar tool for CP2K if needed. Also, you must now the 'history' of
your integral tables (which basis was used when creating them.) If you
by chance used those published on the dftb.org website [2], you can
find the appropriate Slater-coefficients under [1].

  Best regards

    Bálint

[1]  http://www.dftb-plus.info/tools/waveplot/
[2] http://www.dftb.org/

--
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of
Bremen
http://www.bccms.uni-bremen.de/en/~b_aradi