[QE-users] Odd number of electrons yields even total magnetization

[FARAH MARSUSI]

​Dear Carlos,

If everything in your input file is OK, when DFT suffers so much from self interaction error, e.g. for a highly correlated system, this may happen. Please see : " Carbon 144, 615 (2019).


Best wishes,


Farah.

On Tue, 07/16/2019 09:34 AM, "Ayestaran Latorre, Carlos" <carlos.ayestaran-latorre17 at imperial.ac.uk> wrote:
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Hi,


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I have a system consistent of a diamond slab with a boron substitutional defect, an adsorbed hydroxyl and an adsorbed hydrogen on the surface. The system has an odd number of electrons (487) and I run a spin polarized (nspin=2) structural relaxation (see attached).
 One would expect an odd value for the total magnetization, but the it quickly converges to zero.

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I assumed this would be a side effect of smearing allowing partial electronic occupations (I employed gaussian smearing with degauss=0.02). I tried lowering the smearing value down to 0.001, both for gaussian and mv smearing, but only managed to get total magnetization
 ~ 0.3 Bohr mag/cell in both cases. Fixing tot_magnetization=1, however, yields a noticeably higher final energy (~0.3 eV).


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When I run a structural relaxation on a similar system (with an adsorbed H2O molecule instead of the hydroxyl+hydrogen fragments), the total magnetization satisfyingly reaches 1 Bohr mag/cell rather quickly. Other combinations (for example, without the H2O
 molecule at all) also give total magnetization values that don't match the even/odd number of electrons.


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Regards,

Carlos Ayestaran Latorre


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