[Pw_forum] big difference between "total magnetization" and "absolute magnetization" for 4f elements

[mohnish pandey]

Did you try using different initial spin configurations? If your interested
in FM ground state then may be you should try initial magnetic
configuration as FM. e.g. +1, +1 for both.

On Wed, Mar 13, 2013 at 9:03 PM, 琨陶 <taokun76 at gmail.com> wrote:

> Thank you for your suggestions. When I set two atoms in the unit cell
> to be antiferromagnetic, the "total magnetization" is nearly zero, and
> the "absolute magnetization" is about 14.67. And the magnetic moment
> for two atoms are about 7.16 and -7.18, which is more or less
> acceptable.
>
> Now, the question is that why "total magnetization" and "absolute
> magnetization" differs so much if I want to force two atoms into a
> ferromagnetic configuration.
>
> Any suggestions? Thanks!
>
> With regards,
> Kun Tao
>
>
> On 13 March 2013 11:14, Andrei Malashevich <andrei.malashevich at yale.edu>
> wrote:
> > If you want to model antiferromagnetic structure, you should define two
> > types of atoms, Gd1 and Gd2.
> > Change ntyp to 2. Use, e.g.,
> >  starting_magnetization(1)=1.0
> > starting_magnetization(2)=-1.0
> >
> > ATOMIC_SPECIES
> >  Gd1  1.0  Gd.GGA-PBE-paw.UPF
> >  Gd2  1.0  Gd.GGA-PBE-paw.UPF
> > ATOMIC_POSITIONS {crystal}
> > Gd1  0.33333333  0.66666667  0.25
> > Gd2 0.66666667  0.33333333  0.75
> >
> >
> > On Wed, Mar 13, 2013 at 11:05 AM, 琨陶 <taokun76 at gmail.com> wrote:
> >>
> >> Hi,
> >>
> >> Yes, the bulk Gd without Hubbard U is antiferromagnetic. If I set the
> >> two atoms in the unit cell to be antiferromagnetic, the "total
> >> magnetization" should be equal to zero, and the "absolute
> >> magnetization" is what I have gotten. Now, however, the "total
> >> magnetization" is not zero. Could you give me some suggestions?
> >> Thanks!
> >>
> >> With regards,
> >> Kun Tao
> >>
> >> On 13 March 2013 10:48, Stefano de Gironcoli <degironc at sissa.it> wrote:
> >> > are you sure you are defining the correct magnetic structure ?
> >> > is Gd maybe antiferromagnetic ?
> >> > stefano
> >> >
> >> > On 03/13/2013 03:19 PM, 琨陶 wrote:
> >> >> Dear everyone,
> >> >>
> >> >> I want to calculate the magnetic properties of bulk Gd whose magnetic
> >> >> moment is about 8 Bohr magneto/atom. Usually, in the output file
> >> >> values of "total magnetization" and "absolute magnetization" should
> be
> >> >> nearly the same. However, in my output file, I found a big difference
> >> >> between them as following:
> >> >>
> >> >>       total magnetization       =     8.00 Bohr mag/cell
> >> >>       absolute magnetization    =    15.72 Bohr mag/cell
> >> >>
> >> >> The good news is that the "absolute magnetization" is close to the
> >> >> experimental results (7.86 Bohr mag/atom), the bad news is that the
> >> >> "total magnetization" is wrong. Moreover, when I try to calculate the
> >> >> magnetic moment on each atom with projwfc.x program, I got about 4.1
> >> >> Bohr mag/atom.
> >> >>
> >> >> Could you give me some suggestions? Any advice are appreciated,
> thanks!
> >> >>
> >> >> Regards,
> >> >> Kun Tao
> >> >>
> >> >>
> >> >> Attached below is the input file:
> >> >>
> >> >>   &control
> >> >>      calculation='scf'
> >> >>      restart_mode='from_scratch',
> >> >>      prefix='Gd',
> >> >>      pseudo_dir = './'
> >> >>      outdir='./',
> >> >>   /
> >> >>   &system
> >> >>      ibrav= 4, celldm(1)= 6.96, celldm(3)= 1.59,
> >> >>      nat= 2, ntyp=1,
> >> >>      nspin = 2,
> >> >>      starting_magnetization(1)=1.0,
> >> >>      ecutwfc=55.0,
> >> >>      ecutrho=220.0,
> >> >>      occupations ='smearing',
> >> >>      smearing ='gauss',
> >> >>      degauss = 0.01,
> >> >>   /
> >> >>   &electrons
> >> >>      diagonalization='david',
> >> >>      mixing_beta = 0.3,
> >> >>      conv_thr = 1.0d-8,
> >> >>   /
> >> >> ATOMIC_SPECIES
> >> >>   Gd  1.0  Gd.GGA-PBE-paw.UPF
> >> >> ATOMIC_POSITIONS {crystal}
> >> >> Gd  0.33333333  0.66666667  0.25
> >> >> Gd  0.66666667  0.33333333  0.75
> >> >> K_POINTS {automatic}
> >> >> 4 4 4 0 0 0
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-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey,
PhD Student,
Center for Atomic Scale Materials Design,
Department of Physics,
Technical University of Denmark
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