[Wien] LDA+U & External Field
Sherif Yehia
wien542002 at yahoo.com
Fri Oct 24 01:15:34 CEST 2003
Dear Prof. Novak
Thank you very much for directing me to sum both
LDA+U and external field simultaneously your idea work
very nicely.
Now I have in my directory the four needed files to
be summed vorbup/dn_ex and vorbup/dn_U.I am very much
glad that you and prof. Blaha raised the problem of
coupling of spins that really very encouraging and
educative to me. (thanks to both of you).
Our (me and my colleague) interest in exploring the
dependence of the magnetic anisotropy on external
magnetic field have started at some point in our study
of ferromagnetic systems using a simple model that we
used to calculate magnetic properties given the
temperature dependence of both spontaneous
magnetization and anisotropy constants on temperature,
for example the papers :
JMMM 202,565(1999) ; ibid 212,195(2000) on Nd2Fe14B ;
and ibid 222, 368 (2000) on elemental Gd which I
coauthored with my colleague. A paper by F.Ono however
attracted our attention to the field-dependent
anisotropy in Fe ( F.Ono, JMMM. 54-57 (1986)
pp.907-908 ). The author discussed this dependence
theoretically in Refs 1,2 in the aforementioned paper.
According to his theory, part of that dependence comes
from a Fermi level –dependent term which depends on
both of the average magnetic moment and anisotropy
constant at zero field and zero absolute temperature,
on the density of states of the minority spin subband
at EF and on other two terms which are generally of
weak temperature dependence. Therefore we ask the
questions about the possibility of incorporating the
influence of field in ab-initio calculations. Is our
question conceptual? Should one take into account the
possibility that a magnetic field of certain magnitude
and direction may change the symmetry of the crystal
under study?
SmCo5
needs LDA+U with the application of the
external field. I hope with the powerful and
accurate code we have and your stimulating idea I
can learn more about this permenat magnet.
Till I hear your advice and comments
wish you all the best
Sherif Yehia
--- Pavel Novak <novakp at fzu.cz> wrote:
> Dear colleague,
>
> in order to get the two input files for orb, you
> have to create them
> separatelly and then, before running orb, copy
> corresponding file to
> case.inorb:
>
> cp inorb_ex smco5.inorb
> x orb -up
> cp smco5.vorbup vorbup_ex
> cp inorb_U smco5.inorb
> x orb -up
> cp smco5.vorbup vorbup_U
>
> and the same repeat for -dn.
>
> I realized, however, that this is still not enough -
> before running
> x lapwso -up -orb
>
> it is necessary to sum vorbup_ex and vorbup_U
> (similarly dn) and copy the
> sum to smco5.vorbup. To this end a simple program is
> to be written. I am
> interested, so let me know more about your project
> and I could then do it.
>
> Regards Pavel Novak
>
>
>
> On Fri, 17 Oct 2003, Sherif Yehia wrote:
>
> > Dear Prof.Novak
> >
> > Thank you very much for sending that wonderful
> and
> > genius script
> > I started as you advice before
> > 1-SCF using GGA calculation
> > 2-x symmetso
> > 3-x kgen
> > 4-run your Unix script jcontso
> > 5-runsp_lapw -so
> > 6-runsp_lapw -orb -so
> > all the above were done with the following
> smco5.inorb
> > 1 1 0 nmod, natorb, ipr
> > BROYD 0.0 BROYD/PRATT, mixing
> > 1 1 3 iatom nlorb, lorb
> > 1 nsic 0..AFM,
> 1..SIC,
> > 2..HFM
> > 0.39 0.05 U J (Ry)
> >
> > later for mixing Bext calculations
> > I ran vorb and used the following smco5.inorb
> > before using your Bext script
> >
> > 3 1 0 nmod, natorb, ipr
> > PRATT 1.0 BROYD/PRATT, mixing
> > 1 1 3 iatom nlorb, lorb
> > 4. Bext in T
> > 0. 0. 1. Direction Bext in the
> > lattice vector
> >
> > it gave no error but looking at the script
> > it needs these six files
> > 1-vorbup_ext
> > 2-vorbdn_ext
> > 3-vorbup_U
> > 4-vorbdn_ext
> > 5-inorb_ext
> > 6-inorb_U
> > which I didn't get after running vorb up/dn in my
> > working directory although it says the following
> in
> > case.outputorbup/dn
> > calculation of orbital potential for spin block:
> up
> > Type of potential: Interaction with
> Bext
> > Vorb applied to atom 1 orbit. numbers 3
> > end of OP input
> > Bext= 4.00000 T; muB*Bext= 0.17018E-04
> Ry
> >
> > Could you help me please and point my mistake
> with
> > the input for Bext.
> > I still with all the missing files tried to run
> > Bext
> > script. It develop four of the above missing
> files
> > (1-4) I noticed that all have the same data and no
> > change if I ran it for say n cycle
> >
> > Till I hear you kindly advice and comments
> >
> > Thanks very much for help ,support and your
> concern
> >
> > my best wishes and regards
> >
> > Sherif Yehia
> >
> > --- Pavel Novak <novakp at fzu.cz> wrote:
> > > Dear Sherif Yehia,
> > >
> > > present WIEN2k implementation does not allow to
> run
> > > LDA+U and external
> > > magnetic field simultaneously. You can
> circumvent
> > > the problem, however, if
> > > you run orb two times - once for LDA+U, once for
> > > external field and then
> > > use external field potentials in lapw0 and LDA+U
> > > potentials in lapwso. I
> > > never tried that but it should work. An example
> of
> > > the UNIX script, you can
> > > use to this end is attached. Note, however, that
> > > unlike in w2web I mix the
> > > orbital potentials, not the density matrices
> (the
> > > script will be a bit
> > > more simple if density matrices are mixed).
> > >
> > > Regards
> > > Pavel Novak
> > >
> > > On Fri, 10 Oct 2003, Sherif Yehia wrote:
> > >
> > > > Hello All,
> > > > I am working on calculating Magnetic
> Anisotropy
> > > > Energy MAE in SmCo5 I hope to see effect of
> > > external
> > > > magnetic field.
> > > > I would like to ask if the WIEN2k code allow
> for
> > > > LDA+U and an external field to be applied
> > > > simultaneously.
> > > > In the case.inorb file has a switch which
> can
> > > either
> > > >
> > > > call orbital polarization, LDA+U, or an
> external
> > > > magnetic field.(I hope there is another switch
> to
> > > > include both)
> > > >
> > > > In case Wien2k does not do that I would
> welcome
> > > all
> > > > comments ,advice and precaution to develop
> better
> > > > understanding about the reason of not
> including
> > > both
> > > > effects.
> > > >
> > > > Thanks all for efforts and time
> > > >
> > > > Sherif Yehia
> > > >
> > > > Physics Dept
> > > > Helwan Univ.
> > > > Cairo Egypt
> > > >
> > > > __________________________________
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> >
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> > > >
> > > >
> > > > file=$1
> > > num=$2
> > > i=1
> > > while [ $i -le $num ]
> > > do
> > > cp vorbup_ext $file.vorbup
> > > cp vorbdn_ext $file.vorbdn
> > > $HOME/wien2k/x -f $file lapw0
> > > cp $file.clmsum $file.clmsum_old
> > > cp $file.clmup $file.clmup_old
> > > cp $file.clmdn $file.clmdn_old
> > > cp vorbup_ext vorbup_ext_old
>
=== message truncated ===
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