DFTB SKF format in CP2K

[Maicon Lourenco]

Dear all,

Since we are trying to use CP2K to perform SCC-DFTB simulations, I've got some doubts about the second line of the SKF file as it is used in CP2K. For instance, we have the CP2K format and mio format for the pair O-O:

CP2K style:

0.02, 500,2
0.0 -0.33213167 -0.87883246, -0.05414, 0.0  0.5222   0.5564 0.0 4.0 2.0 *T
0.467495  0.523305*
16.01,  19*0.0,

DFTB (mio) style:

0.02, 500,2
0.0 -0.33213167 -0.87883246, -0.05414, 0.467495  0.523305   0.4954 0.0 4.0
2.0
16.01,  19*1.0,
20*1.0,

As far as we know, the meaning of the second line of the SKF is:
d, p, s (valence atomic orbital energies), "spin polarization error", d, p, s (Hubbard parameter), d, p, s (valence orbital occupation).
However, we do not get the order of the values in the second line of the CP2K O-O parameter and mainly the meaning of the "*T 0.467495  0.523305*".

Another thing is, why is the "0.0" after the 0.05414 since it is not there in the mio format?

As we need to use the mio format, how can I do that to use it properly in CP2K? We have observed some considerable total energy differences when the "T ..." is not present in the second line. How can I set that correctly?

Thank you very much!

Maicon Pierre Lourenço

[hut...@chem.uzh.ch]

Hi

CP2K reads the second line of the SKF files in the following format:

d,p,s (orb energy), energy, d,p,s (Hubbard), d,p,s, (occupation)

the rest of the line is ignored. The energy value is not used.
The two examples have both no d orbitals and therefore we can also
ignore the d Hubbard value.

The mio style files should work also in CP2K, but
make sure that you only use the same basis (sp vs. spd),
that you only use a single Hubbard value (no multiple values allowed in CP2K)
that you are not using additional options like DFTB3.

Another possible source of errors is the definition of the repulsion potential.
CP2K defines the potential from the SKF file, while other programs do this
through the input.
Check for the value of "Repulsive potential energy:"

regards

Juerg Hutter

--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut...@chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

-----cp...@googlegroups.com wrote: -----To: cp2k <cp...@googlegroups.com>
From: Maicon Lourenco
Sent by: cp...@googlegroups.com
Date: 02/23/2016 06:01PM
Subject: [CP2K:7451] DFTB SKF format in CP2K

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[Maicon Lourenco]

Juerg Hutter,

thank you very much for your answer.

It helped a lot. We still did not solve completely the problem. But, after we get the solution, we will comment on the forum about it.

All the best,

Maicon P. Lourenço

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