[QE-users] occupation=smearing and magnetic moment

[mkondrin]

On 15.04.2021 20:01, Evgeny Permyakov wrote:
> Interesting. With degauss = 1.0e-2 I get zero magnetisation, with degauss =
> 3.1e-3 I get 0.5 Bohr magnetisation. That's a quite small value, IMHO. Is
> it normal?

degauss value is equal to 1.0e-2 Ry == 0.01*13.6*1000*11.6 = 1500 K. Not so small value if compared to typical Curie temperature of strong ferromagnets (Fe, Ni). However, DFT usually overestimates magnetic ordering (the figures are order of magnitude larger). So, I believe you should further decrease degauss value to achieve correspondence with the "true" value obtained during "fixed" calculations.

  


>
> On Thu, 15 Apr 2021 at 14:41, mkondrin <mkondrin at hppi.troitsk.ru> wrote:
>
>> On 15.04.2021 15:23, Evgeny Permyakov wrote:
>>> Dear QE users! I found that the calculated magnetic moment of the minimal
>>> cell of LaFe4P12  depends on whether I use occupations=smearing,
>>> specifically I get magnetisation about 2.7 Bohr/cell for
>> occupations=fixed
>>> and zero magnetisation for occupations=smearing. Is it normal? Why does
>> it
>>> even happen? What result is the more 'correct' one?
>>>
>>> The system is suspected to be a Pauli paramagnet, does this fact mess
>>> somehow the calculation and how should I approach modeling it?
>>>
>>> I added the minimal input file to reproduce the behaviour.
>>>
>>>
>>>
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>> Hi, Evgeny!
>>
>> This can happen if you choose large smearing parameter. So the smearing
>> is larger than the energy splitting induced by magnetization. Try to
>> decrease degauss value.
>>
>> Yours,
>> M. V. Kondrin
>> _______________________________________________
>> 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
>>
>
>
> _______________________________________________
> 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