[CP2K:2018] Re: electron density cube file after DFTB

[Juerg Hutter]

Hi

of course you are right. You can plot a density in the way
you are describing. My remark was more of a general nature.

For example it is possible to have different basis functions
for C-H and C-O parameters (might not be a good idea, but the
method allows for it). The electron density is not directly
linked to the electrostatic potential used (also true for SCC-DFTB)
or is relevant for the XC energy.

Still, it might give some insight in the chemistry of your system.

regards

Juerg Hutter

----------------------------------------------------------
Juerg Hutter                   Phone : ++41 44 635 4491
Physical Chemistry Institute   FAX   : ++41 44 635 6838
University of Zurich           E-mail: hut... at pci.uzh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
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On Mon, 20 Apr 2009, Bálint Aradi wrote:

>
> 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
> >
>