[Pw_forum] Relation between cell magnetization and atomic magnetization in the non-collinear calculation

[Giovani Faccin]

Dear Guido,

Thank you very much!

Giovani


2012/1/9 Guido Fratesi <fratesi at mater.unimib.it>

> Dear Giovani,
>
> the unit cell is not 100% filled by the atom-centered spheres where the
> quantities of your interest are computed. Notice that also the sum of
> the atomic charges (11) is different than the cell one (16?).
>
> For information about such spheres, you might want to have a look in the
> output file to something like:
>
>      Generating pointlists ...
>      new r_m :   0.3457 (alat units)  1.8649 (a.u.) for type    1
>
> and the subroutine in PW/make_pointlists.f90. From that file:
>
>   ! This initialization is needed in order to integrate charge (or
>   ! magnetic moment) in a sphere around the atomic positions.
>   ! This can be used to simply monitor these quantities during the scf
>   ! cycles or in order to calculate constrains on these quantities.
>   !
>   ! If the integration radius r_m is not provided in input, it is
>   ! calculated here. The integration is a sum over all points in real
>   ! space with the weight 1, if they are closer than r_m to an atom
>   ! and 1 - (distance-r_m)/(0.2*r_m) if r_m<distance<1.2*r_m
>
> HTH,
> Guido
>
> Il 01/09/2012 01:49 PM, Giovani Faccin ha scritto:
> > Dear PW-Users,
> >
> > While performing a test calculation for a non-collinear Fe2 dimer
> > without spin-orbit, I get the following results (just printing the
> > relevant part):
> >
> >
> >
> ==============================================================================
> >       atom number    1 relative position :    0.1234   0.0000   0.0000
> >       charge :     5.500331
> >       magnetization :          0.000000    0.000000    2.549039
> >       magnetization/charge:    0.000000    0.000000    0.463434
> >       polar coord.: r, theta, phi [deg] :     2.549039    0.000000
> > 360.000000
> >
> >
> ==============================================================================
> >
> >
> ==============================================================================
> >       atom number    2 relative position :    0.0001   0.0000   0.0000
> >       charge :     5.500187
> >       magnetization :          0.000000    0.000000    2.548980
> >       magnetization/charge:    0.000000    0.000000    0.463435
> >       polar coord.: r, theta, phi [deg] :     2.548980    0.000000
> > 360.000000
> >
> >
> ==============================================================================
> >
> > (little more output here, then)
> >
> >      total magnetization       =     0.00     0.00     6.00 Bohr mag/cell
> >       absolute magnetization    =     6.36 Bohr mag/cell
> >
> >
> > The cell magnetization prints 6.0 Bohr/cell, which is the expected
> > result. However, the atomic magnetization prints 2.549039 + 2.548980 ~
> > 5.10 mB.
> >
> > I'm wondering: why is not the atomic magnetization sum equal (or very
> > close to) the cell magnetization? If needed, the input file is attached.
> >
> > Thanks in advance.
> >
> > Giovani Faccin
> > UFMS / Brazil
> >
> >
> >
> >
> >
> >
> >
> >
> > Giovani
> >
> >
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>
> --
> Guido Fratesi
>
> Dipartimento di Scienza dei Materiali
> Universita` degli Studi di Milano-Bicocca
> via Cozzi 53, 20125 Milano, Italy
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