[CP2K-user] [CP2K:21571] Halogen correction and XTB file?

[Jürg Hutter]

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: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Andreas Döll <andreasm.doell 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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