[QE-users] Help in spin polarized calculation for surface dangling bonds

[Lorenzo Sponza]

Thanks Giovanni for your quick answer.

Still, it's not clear to me how to set the starting magnetization. 
Putting just starting_magnetization=X will be useless because this will 
set a starting magnetization in all Si atoms, that will break no 
symmetry.
On the other hand, if I understood well I can define two atomic species, 
say Si1 and Si2, and define the starting magnetization for only one of 
the two. I think that this is the thing I should do, but I can not 
figure out which atoms should belong to one group or the other and 
wheather I need more than two groups for this specific problem.
I was hoping to get help from someone who had already done similar 
simulations.
Cheers

Le 2025-04-19 17:25, Giovanni Cantele a écrit :
> Dear Lorenzo,
> 
> the variable starting_magnetization is usually used to drive the
> system
> out of the non magnetic solution, in that starting_magnetization(i) =
> 0 for all atomic species
> should always bring to a spin unpolarized system. The starting value
> in some cases is not so important
> (different values will produce the same magnetic ground state), but as
> far as I remember it could be
> in some (not so frequent) cases where different magnetic energy minima
> exist.
> 
> For the other questions:
> - no special attention paid to the pseudopotential choice, if you mean
> to choose a pseudopotential "specific"
> for a spin-polarized calculation
> - I would not use the input_DFT variable unless you need it for
> specific purposes (e.g. non local functionals, like vdw-DF).
> 
> Ciao,
> Giovanni
> 
> --
> 
> Giovanni Cantele, PhD
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> e-mail: giovanni.cantele at spin.cnr.it
> Phone: +39 081 676910
> Skype contact: giocan74
> 
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009
> Web page: https://sites.google.com/view/giovanni-cantele/home
> 
> Il giorno sab 19 apr 2025 alle ore 16:37 Lorenzo Sponza
> <lorenzo.sponza at onera.fr> ha scritto:
> 
>> Dear Quantum ESPRESSO users and developpers,
>> 
>> I need some help to set up a calculation of a Si(111) 1x1 surface.
>> This
>> surface is characterized by dangling bonds that spoil the electronic
>> 
>> states around Fermi. In literature, two approaches are usually
>> adopted.
>> One consists in saturating the surface with H atoms, the other
>> consists
>> in performing a spin polarized calculation.
>> I want to give both methods a try, but I stuck when it comes to set
>> up
>> the spin polarized input file. I set nspin=2, but I'm perplexed
>> about
>> the value to give to starting_magnetization since I have only Si
>> atoms
>> here, and in this specific case it is not clear to me how this
>> variable
>> is interpreted and used by the code.
>> Finally, is there any attention to be paid in choosing the
>> pseudopotential or in specifying the input_DFT variable? I've used
>> PBE
>> scalar relativistic PAW pseudos so far.
>> 
>> Many thanks for your help.
>> 
>> --
>> Dr. Lorenzo Sponza
>> 
>> Chargé de Recherche au CNRS
>> Université Paris-Saclay, ONERA, CNRS Laboratoire d'étude des
>> microstructures (LEM)
>> 29 Avenue de la division Leclerc, 92322 Châtillon
>> Tel: +33146734464
>> 
>> ETSF Research Team Leader
>> European Theoretical Spectroscopy Facility
>> 17 Sart-Tilman B-4000 Liège, Belgium
>> 
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> 
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> _______________________________________________________________________________
> The Quantum ESPRESSO Foundation stands in solidarity with all
> civilians worldwide who are victims of terrorism, military aggression,
> and indiscriminate warfare.
> --------------------------------------------------------------------------------
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> users mailing list users at lists.quantum-espresso.org
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-- 
Dr. Lorenzo Sponza

Chargé de Recherche au CNRS
Université Paris-Saclay, ONERA, CNRS Laboratoire d'étude des 
microstructures (LEM)
29 Avenue de la division Leclerc, 92322 Châtillon
Tel: +33146734464

ETSF Research Team Leader
European Theoretical Spectroscopy Facility
17 Sart-Tilman B-4000 Liège, Belgium