[Pw_forum] magnetism issues

Samin, Adib J. samin.2 at buckeyemail.osu.edu
Tue Jul 1 16:25:19 CEST 2014


Hello all,


I am trying to calculate the total magnetization and the magnetic moments per atom of iron neodymium boron (NdFeB). The unit cell contains 68 atoms. I first checked convergence with respect to the energy cutoff (to within 1mRy/atom), the k-points, and the number of bands used. The PBE Generalized Gradient exchange correlation functional was used in a spin-polarized calculation. Two separate calculations were performed. In the first calculation no Hubbard U was used and in the second calculation, Hubbard U values were used for both the Nd and Fe atoms to account for the repulsion between localized electrons. I have attached my input file below for the latter case. It is interesting that when I use the Hubbard U, I obtain the "correct" total magnetization which agrees with the literature but the magnetic moments are totally wrong. What is specifically alarming is that the Nd and Fe magnet moment are oriented antiparallel in the Hubbard U calculation (and this is wrong). Without using the Hubbard U, the magnetic moments are parallel to each other but the total magnetization and the individual magnetic moments are still off. Any help with this issue would be greatly appreciated.


&control

    calculation='scf'

    restart_mode='from_scratch',

    wf_collect=.TRUE.,

    prefix='NdFeB',

    pseudo_dir = '/usr/local/espresso/espresso-5.0.3/pseudo/',

    outdir = '/fs/lustre/osu7834/NdFeB/'

/

&system

    ibrav=0, nat=68, ntyp=3,

    nspin=2, starting_magnetization(1)=0.6, starting_magnetization(2)=0.6, starting_magnetization(3)=0.6,

    ecutwfc = 260.0

    occupations='smearing', smearing='mv', degauss=0.002

    lda_plus_u=.true.

    Hubbard_U(1)=6.0, Hubbard_U(2)=2.9

/

&electrons

    conv_thr=1.0e-6

    mixing_beta=0.02

    mixing_mode = 'local-TF'

/

CELL_PARAMETERS {angstrom}

8.8 0.0 0.0

0.0 12.19 0.0

0.0 0.0 8.8

ATOMIC_SPECIES

Nd  144.24   Nd.pbe-mt_fhi.UPF

Fe  55.845   Fe.pbe-mt_fhi.UPF

B   10.811   B.pbe-mt_fhi.UPF

ATOMIC_POSITIONS {angstrom}

B       5.54400     0.00000     3.25600

B       3.25600     0.00000     5.54400

B       7.65600     6.09500     7.65600

B       1.14400     6.09500     1.14400

Fe      4.40000     0.00000     0.00000

Fe      4.40000     6.09500     0.00000

Fe      0.00000     6.09500     4.40000

Fe      0.00000     0.00000     4.40000

Fe      4.40000     1.37747     4.40000

Fe      0.00000     7.47247     0.00000

Fe      0.00000     4.71753     0.00000

Fe      4.40000    10.81253     4.40000

Fe      0.85360     2.49895     0.85360

Fe      7.94640     2.49895     7.94640

Fe      5.25360     8.59395     3.54640

Fe      3.54640     8.59395     5.25360

Fe      5.25360     3.59605     3.54640

Fe      3.54640     3.59605     5.25360

Fe      0.85360     9.69105     0.85360

Fe      7.94640     9.69105     7.94640

Fe      2.79840     3.01093     2.79840

Fe      6.00160     3.01093     6.00160

Fe      7.19840     9.10593     1.60160

Fe      1.60160     9.10593     7.19840

Fe      7.19840     3.08407     1.60160

Fe      1.60160     3.08407     7.19840

Fe      2.79840     9.17907     2.79840

Fe      6.00160     9.17907     6.00160

Fe      4.99840     1.56032     1.97120

Fe      3.80160     1.56032     6.82880

Fe      6.37120     7.65532     8.20160

Fe      2.42880     7.65532     0.59840

Fe      0.59840     4.53468     2.42880

Fe      8.20160     4.53468     6.37120

Fe      1.97120    10.62968     4.99840

Fe      6.82880     1.56032     3.80160

Fe      3.80160    10.62968     6.82880

Fe      4.99840    10.62968     1.97120

Fe      2.42880     4.53468     0.59840

Fe      6.37120     4.53468     8.20160

Fe      8.20160     7.65532     6.37120

Fe      0.59840     7.65532     2.42880

Fe      6.82880    10.62968     3.80160

Fe      1.97120     1.56032     4.99840

Fe      3.15920     2.14544     0.34320

Fe      5.64080     2.14544     8.45680

Fe      4.74320     8.24044     1.24080

Fe      4.05680     8.24044     7.55920

Fe      7.55920     3.94956     4.05680

Fe      1.24080     3.94956     4.74320

Fe      0.34320    10.04456     3.15920

Fe      8.45680     2.14544     5.64080

Fe      5.64080    10.04456     8.45680

Fe      3.15920    10.04456     0.34320

Fe      4.05680     3.94956     7.55920

Fe      4.74320     3.94956     1.24080

Fe      1.24080     8.24044     4.74320

Fe      7.55920     8.24044     4.05680

Fe      8.45680    10.04456     5.64080

Fe      0.34320     2.14544     3.15920

Nd      2.34080     0.00000     2.34080

Nd      6.45920     0.00000     6.45920

Nd      6.74080     6.09500     2.05920

Nd      2.05920     6.09500     6.74080

Nd      7.56800     0.00000     1.23200

Nd      1.23200     0.00000     7.56800

Nd      5.63200     6.09500     5.63200

Nd      3.16800     6.09500     3.16800



K_POINTS {automatic}

4 4 4 0 0 0



Adib Samin

Graduate Fellow

The Department of Mechanical and Aerospace Engineering

The Ohio State University




-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20140701/752627f1/attachment.html>


More information about the users mailing list