[QE-users] Question on using bands.x with nspin=2 and total_magnetization=1

[Rameswar Bhattacharjee]

Dear QE community,

I would greatly appreciate your advice on this. Basically, I am trying to
perform a band structure calculation for a unit cell that contains an
unpaired electron and is therefore paramagnetic. Could you please suggest
the proper way to handle this setup?

Thank you for your guidance.

Best regards,

On Sun, Aug 31, 2025 at 5:03 PM Rameswar Bhattacharjee <
rb1820 at georgetown.edu> wrote:

> Dear Dr Paulatto,
> Thank you very much for your response. Actually, the error I am getting is
> as below'
>
> ---------------------------------------------------------
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      Error in routine bands (1):
>     The bands code with constrained magnetization has not been tested
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> --------------------------------------------------------
>
> And I was wrong earlier, the error also appears even if I do not use
> spin_component. I think this error shows as I have "total_magnetization=1"
> in my scf input.  Now, my system has -2 charge and the spin multiplicity is
> 2.  When I used starting_magnetization instead of total_magnetization, all
> the calculations were fine but I did not get the right magnetic moment as I
> expected.
>
> Basically, I did an scf, nscf, bands and then used a post procession
> calculation using bands.x to generate the ".dat" file for the band
> structure. The first three job competed successfully and the error appears
> only in the last post procession calculation for which the input is below:
>
> ---------------
>
> &BANDS
>
>   prefix = 'crystal_from_cif',
>
>   outdir='./scratch'
>
>   filband = 'bands.dat'
>
> /
> ---------------
>
> I am also attaching the other inputs for you to take a quick look. Please
> note that the coordinates are not complete in the inputs
>
> I am also curious to know about your comment above "It depends on what you
> want to achieve." Could you please elaborate this a bit more?
>
> Your advice would be highly appreciated.
>
> Thanks
> Rameswar
>
> On Sun, Aug 31, 2025 at 3:54 PM Lorenzo Paulatto <lorenzo.paulatto at cnrs.fr>
> wrote:
>
>>
>>
>>    -
>>
>>    Should I use the spin_component keyword to specify up-spin or
>>    down-spin bands, or is it recommended to simply run bands.x without
>>    this keyword?
>>
>> It depends on what you want to achieve.
>>
>>
>>    -
>>
>>    I tried using spin_component=1 and 2, but I encountered errors in
>>    both cases. On the other hand, when I ran bands.x without the
>>    spin_component keyword, the job completed normally.
>>
>> Which error?
>>
>> Could you please advise on the correct way to handle this situation? Any
>> guidance or clarification would be greatly appreciated.
>>
>> The correct way is to provide the full input and output of the
>> calculation that is giving you trouble. And, more in general, if you think
>> that a specific output is wrong, you should explain why you think so.
>>
>> kind regards
>>
>> Thank you in advance for your help.
>>
>> Best regards,
>> Rameswar Bhattacharjee
>>
>> --
>> Rameswar Bhattacharjee
>> Georgetown University
>> Washington, DC 20057
>>
>> _______________________________________________________________________________
>> 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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>>
>> --
>> Dr. Lorenzo Paulatto
>> IR IMPMC - CNRS UMR 7590 / Sorbonne Université / MNHN
>> phone: +33 (0)1 442 79822 / telegram: lpaulatto
>> http://www.impmc.upmc.fr/~paulatto/ - https://anharmonic.github.io/
>> 23-24/423 B115, 4 place Jussieu 75252 Paris CX 05
>>
>> _______________________________________________________________________________
>> The Quantum ESPRESSO Foundation stands in solidarity with all civilians
>> worldwide who are victims of terrorism, military aggression, and
>> indiscriminate warfare.
>>
>> --------------------------------------------------------------------------------
>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
>> users mailing list users at lists.quantum-espresso.org
>> https://lists.quantum-espresso.org/mailman/listinfo/users
>
>
>
> --
> Rameswar Bhattacharjee
> Georgetown University
> Washington, DC 20057
>


-- 
Rameswar Bhattacharjee
Assistant Research Professor
Department of Chemistry
Georgetown University
Washington, DC 20057
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