DFTB3 and DFTB-D3

[Linc]

Dear CP2K developers/users,

I noticed that since version 2.6 CP2K has incorporated the 3rd order correction to DFTB and also included the D3 dispersion corrections. Just to make sure I understand the implementation correctly, I wish to ask the following two questions.

(1) The function for damping hydrogen bonds takes the form of exp[ -((U_a+U_b)/2)^HB_SR_PARAM * r_ab ]. If I want to use the 3OB Slater-Koster files, then HB_SR_PARAM should be 4.0 as specified by the 3OB parameter set. But, the question is: if/how can I define the Hubbard parameters U_a and U_b? I guess CP2K has default values for them, but would it be possible to specify them by the user? FYI, Eq. 7 in J. Chem. Theory Comput., 2013, 9 (1), pp 338.

(1) Regarding the D3 corrections for DFTB, can I assume that the dftd3.dat file, provided under ./cp2k-2.6.0/data/, contain the DFTB-compatible parameters as used by S. Grimme in J. Phys. Chem. Lett., 2014, 5 (11), pp 1785 (if there are such parameters at all - sorry, haven't gone through all the relevant literature).

Many thanks in advance for any information/help on these questions!

Best regards,

Linc

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

Hi

- for the hydrogen bond damping you have the parameter
HB_SR_GAMMA in the DFTB section of the input. The U_a and U_b
parameters in your formula come directly from the SK files
(eta(0)).

- For the DFTB3 correction (DIAGONAL ONLY!!!!) the parameters can
be set in the KIND section (DFTB3_PARAM).

- The vdW D3 correction reads parameters from dftd3.dat, this is
an adaptation of the official file by Grimme.
You can change the settings of the parameters in the input from
the DFTB/PARAMETER section.
However, only the original damping function is available (no BJ-damping)
and C9 terms are switched off.

regards

Juerg

--------------------------------------------------------------
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: cp...@googlegroups.com
From: Linc
Sent by: cp...@googlegroups.com
Date: 02/12/2015 12:57AM
Subject: [CP2K:6090] DFTB3 and DFTB-D3

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[Linc]

Thank you so very much Juerg!