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

[José Carlos Conesa Cegarra]

Hi,

Sodium metal has an odd number of electrons per primitive unit cell 
(which contains a single atom), and however is nonmagnetic. The same 
applies to aluminum. This is the result of having a large overlap 
between orbitals, making the (in principle) spin up and spin down energy 
separation much smaller than the bandwidth so that spin up and down 
electrons are equaled in population. Did you verify whether this is your 
case?

Regards,

José Carlos

El 16/07/2019 a las 15:34, Ayestaran Latorre, Carlos escribió:
> 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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