[CP2K-user] [CP2K:21576] Halogen correction and XTB file?

[Jürg Hutter]

Hi

for RESP charges you have to use DFT. If you don't like the results, investigate if basis sets and/or xc functionals are
appropriate.
Other charge methods available are: Mulliken/Lowdin, Hirshfeld, Mulliken-from-IAO, MAO analysis, ...

In xTB (gfn0/1/2) atomic charges are part of the functional definition, no need to extra calculate them.

For correct input files, see the test/QS and test/xTB directories.

regards
JH

________________________________________
From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Andreas Döll <andreasm.doell at gmail.com>
Sent: Tuesday, June 24, 2025 7:05 PM
To: cp2k
Subject: Re: [CP2K:21573] Halogen correction and XTB file?

Hello,

Thank You for Your fast response! Even without including RESP section my input file is faulty, so how can I correct it? I want to understand cp2k more, so even if I will not use the xTB in the end, I would like to learn!

Additionally, would other charge methods like Hirsch or mullikan be available when using halogen corrections? On another note, is it possible to include some other corrections to still use RESP charges (which I would strongly prefer) to make the charges on Br more realistic? Any tricks?

Thank you in advance!

Cheers,
Andreas

Jürg Hutter schrieb am Dienstag, 24. Juni 2025 um 16:14:58 UTC+2:
Hi

you are calculating RESP charges for a KS-DFT method. Halogen corrections are a thing for tight-binding methods.
You can't mix the two methods and you can't calculate RESP charges from xTB.

regards
JH

________________________________________
From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of Andreas Döll <andreas... at gmail.com>
Sent: Tuesday, June 24, 2025 3:49 PM
To: cp2k
Subject: [CP2K:21571] Halogen correction and XTB file?

Dear Cp2k community,

I want to calculate the RESP charges for a benzene ring with 2 Bromium atoms. Attached is my input script resp.inp, which worked so far for small molecules. However, I noticed that the magnitude of the partial charge is quite low for Br (q_i=-0.099), so I read up online and found that you need to include Halogen corrections to properly capture Br in particular, see the related paper Grimme 2017 from the cp2k website. In cp2k this is done via &XTB section and the USE_HALOGEN_CORRECTION keyword, correct?

I tried using the following section:

&XTB
COULOMB_INTERACTION T
TB3_INTERACTION F
CHECK_ATOMIC_CHARGES F
DO_EWALD T
USE_HALOGEN_CORRECTION T
&PARAMETER
DISPERSION_PARAMETER_FILE dftd3.dat

PARAM_FILE_NAME xTB0_parameters
&END PARAMETER
&END XTB

But there are multiple points where I am failing:

The most important point is that I need a xTB_parameters file, but the only file I could find in cp2k repository was the xTB0_parameters file which begins with $info and every time I include it in my script, it says that $info as variable is not defined. However, as far as I understand I need some kind of file for the corrections, or no? If so where can I get the correct file?

Second, am I even using the use_halogen_correction keyword correctly? In the end I want more realistic RESP charges for my molecule, especially on Bromium.

I am very unfamiliar with xtb, so probably this is a very basic question. If you have any other input, I appreciate it as well! I attach my molecule xyz file as well as every other file for testing.

Thank you very much in advance!

Sincerely,
Andreas Doell


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