[CP2K-user] [CP2K:22269] Spin polarized calculation with xTB

[Michael LaCount]

I looked into this earlier this year.

Tblite does seem to support the spin polarized version (spGFNn) see 
https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/jcc.27185 "All 
(sp)GFNn-xTB calculations were performed with the tblite v. 0.3.0 
development version either as a standalone or in the xtb v. 6.5.1 
development version." A bit ambiguous but it seems to me to read like 
tblite supported spGFN-xTB.

But I'll note that I found using LSD with TBLITE GFN1 doesn't work properly 
(at least in v2026.1) (see https://github.com/cp2k/cp2k/issues/4818 and 
https://github.com/cp2k/cp2k/pull/4804). Also TBLITE with GFN2 has (or at 
least had) some odd behavior assigning electrons for nitrogen.

In short, at least as of CP2K 2026.1 there is no way (to my knowledge) to 
get a proper spGFNn calculation done with CP2K. The best you can do is 
triplet GFN0/1 using the internal CP2K implementation of XTB.

Best,
Michael

On Monday, June 8, 2026 at 7:12:08 AM UTC-7 Jürg Hutter wrote:

> Hi
>
> This extension is not included in the CP2K native gfn0/1 xTB Hamiltonians.
>
> I don't know if it is available through tblite, but most likely it has to 
> be triggered by a
> keyword and defaults to the original spinless Hamiltonian.
> Probably this keyword is not yet accessible through the CP2K input?
>
> best regards
> JH
>
> ________________________________________
> From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of Dmitry 
> Ryndyk <dmitry... at tu-dresden.de>
> Sent: Monday, June 8, 2026 3:36 PM
> To: cp2k
> Subject: Re: [CP2K:22267] Spin polarized calculation with xTB
>
> Dear all,
>
> What is going on at present?
>
> The xTB site<
> https://xtb-docs.readthedocs.io/en/latest/spgfn.html#spgfnn-xtb> states 
> that spin-polarized calculations with tblite are possible, and 
> spin-dependent Hamiltonians are described in the 2023 paper<
> https://onlinelibrary.wiley.com/doi/10.1002/jcc.27185>.
>
> Moreover, at the CP2K site<
> https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/QS/XTB/TBLITE.html>, 
> it is written:
> Spin-polarized CP2K/tblite calculations are selected with the regular 
> DFT/UKS keyword or its LSD/SPIN_POLARIZED aliases; DFT/MULTIPLICITY sets 
> the number of unpaired electrons. UKS uses tblite’s spin-polarized 
> Hamiltonian.
>
> At the moment, however, it seems to be blocked. One always gets restricted 
> orbitals.
> Any ideas?
>
> Best wishes,
> Dmitry
>
> hut... at chem.uzh.ch schrieb am Freitag, 5. März 2021 um 19:09:23 UTC+1:
> Hi
>
> you can calculate a triplet using UKS. For xTB the results should
> show equal orbital energies for alpha and beta spin, even though
> the occupations will be different.
>
> regards
>
> Juerg
> --------------------------------------------------------------
> Juerg Hutter Phone : ++41 44 635 4491 <+41%2044%20635%2044%2091>
> <tel:+41%2044%20635%2044%2091>
> Institut für Chemie C FAX : ++41 44 635 6838 <+41%2044%20635%2068%2038>
> <tel:+41%2044%20635%2068%2038>
> Universität Zürich E-mail: hut... at chem.uzh.ch
> Winterthurerstrasse 190
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----cp... at googlegroups.com wrote: -----
> To: cp... at googlegroups.com
> From: "Pierre-André Cazade"
> Sent by: cp... at googlegroups.com
> Date: 03/05/2021 05:16PM
> Subject: Re: [CP2K:14885] Spin polarized calculation with xTB
>
> Dear Juerg,
>
> It's a very interesting topic. Provided what you described in your reply, 
> is it possible to use xTB for a triplet state? If yes, is it necessary to 
> use UKS, since the Hamiltonian doesn't have spin-dependence?
>
> Regards,
> Pierre
> On Fri, Mar 5, 2021 at 3:42 PM <hut... at chem.uzh.ch> wrote:
> Hi
>
> you can use unrestricted calculations also with xTB. However,
> the xTB Hamiltonian doesn't have a spin dependence. So what you
> get is the same as using a restricted open shell calculation.
> Unrestricted is double the work, but can use OT methods.
> Restricted open shell (ROKS will not work btw) will need
> diagonalization and smearing. What is more efficient in the end
> might depend on your system.
>
> best regards
>
> Juerg Hutter
> --------------------------------------------------------------
> Juerg Hutter Phone : ++41 44 635 4491 <+41%2044%20635%2044%2091>
> <tel:+41%2044%20635%2044%2091>
> Institut für Chemie C FAX : ++41 44 635 6838 <+41%2044%20635%2068%2038>
> <tel:+41%2044%20635%2068%2038>
> Universität Zürich E-mail: hut... at chem.uzh.ch
> Winterthurerstrasse 190
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----cp... at googlegroups.com wrote: -----
> To: "cp2k" <cp... at googlegroups.com>
> From: "Mauro Sgroi"
> Sent by: cp... at googlegroups.com
> Date: 03/05/2021 09:33AM
> Subject: [CP2K:14881] Spin polarized calculation with xTB
>
> Dear all,
> I'm trying to understand if it is possible to use xTB to perform spin 
> polarized calculations.
> If yes, which is the right way to proceed?
> Is there an howto to follow?
>
> Thannks a lot and best regards,
> Mauro Sgroi
> Centro Ricerche FIAT
> Italy
>
> --
> You received this message because you are subscribed to the Google Groups 
> "cp2k" group.
> To unsubscribe from this group and stop receiving emails from it, send an 
> email to cp2k+uns... at googlegroups.com.
> To view this discussion on the web visit 
> https://groups.google.com/d/msgid/cp2k/f6049f47-2a0d-4d21-bdd7-8a1fa320dfb3n%40googlegroups.com
> .
>
>
> --
> You received this message because you are subscribed to the Google Groups 
> "cp2k" group.
> To unsubscribe from this group and stop receiving emails from it, send an 
> email to cp2k+uns... at googlegroups.com.
> To view this discussion on the web visit 
> https://groups.google.com/d/msgid/cp2k/OFDF4C8D2B.FF7BE2D3-ONC125868F.0056498D-C125868F.0056498E%40lotus.uzh.ch
> .
>
> --
> You received this message because you are subscribed to the Google Groups 
> "cp2k" group.
> To unsubscribe from this group and stop receiving emails from it, send an 
> email to cp2k+uns... at googlegroups.com.
> To view this discussion on the web visit 
> https://groups.google.com/d/msgid/cp2k/CAFnf9gqvD3jnN_wRAgbYZGaN%2BC1%2BGANJHs8-Nqf-ruYMGjKHHQ%40mail.gmail.com
> .
>
>
> --
> You received this message because you are subscribed to the Google Groups 
> "cp2k" group.
> To unsubscribe from this group and stop receiving emails from it, send an 
> email to cp2k+uns... at googlegroups.com<mailto:cp2k+uns... at googlegroups.com
> >.
> To view this discussion visit 
> https://groups.google.com/d/msgid/cp2k/05c0af2b-f6cb-4bdb-817c-521bcf5acfb9n%40googlegroups.com
> <
> https://groups.google.com/d/msgid/cp2k/05c0af2b-f6cb-4bdb-817c-521bcf5acfb9n%40googlegroups.com?utm_medium=email&utm_source=footer
> >.
>

-- 
You received this message because you are subscribed to the Google Groups "cp2k" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+unsubscribe at googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/cp2k/25710ec6-ea83-4356-80e3-69a6dfae4d27n%40googlegroups.com.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20260608/8d077472/attachment-0001.htm>