[CP2K-user] [CP2K:22267] Spin polarized calculation with xTB

[Dmitry Ryndyk]

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>
> Institut für Chemie C FAX : ++41 44 635 6838 <+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>
> Institut für Chemie C FAX : ++41 44 635 6838 <+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
>
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