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

[Ayestaran Latorre, Carlos]

Hi,

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.

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).

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.

Regards,
Carlos Ayestaran Latorre



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