[Pw_forum] A question on atomic magnetic moments
Giovani Faccin
faccin.giovani at gmail.com
Mon Feb 14 05:31:52 CET 2011
Hi Duy Le,
Thanks for the idea. Tried it, and this is what I got:
Imposed Magnetization | Total Energy (Hartree)
5.0
5.2
5.4
5.6 -55.527688685
5.8 -55.533921200
6.0 -55.540351250
6.2 -55.540980910
6.4 -55.541296415
6.6
6.8
7.0
7.2
Values in blank are simulations that didn't execute, with the following
error message:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
task # 0
from set_nelup_neldw : error # 2
tot_magnetization is inconsistent with total number of electrons
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
So two interesting facts appeared here:
1 - The energy minimum does not converge to 6, as it should do;
2 - When an unconstrained magnetization is used, the magnetization converges
to a value around 6.82. However, If I try to impose this value as a fixed
magnetization from start, pw.x won't even begin the calculation. Weird,
isn't it?
I'm posting below a sample input file used for this battery of tests. I've
used a smaller cell size here to speed things up a little. If celldm(1) is
increased say to 40 instead of 25, you'll get a change in magnetic moment of
about 0.05 mB. This is probably irrelevant as far as finding the cause of
these results is concerned.
Any other suggestions, just tell me; I'll try it and report back.
======================
&CONTROL
calculation = 'scf' ,
restart_mode = 'from_scratch' ,
wf_collect = .true. ,
outdir = './output' ,
pseudo_dir = '../pseudo/' ,
prefix = 'fe' ,
etot_conv_thr = 1.0D-9 ,
forc_conv_thr = 1.0D-6 ,
tstress = .true. ,
tprnfor = .true. ,
/
&SYSTEM
ibrav = 1,
celldm(1) = 25,
nat = 2,
ntyp = 1,
ecutwfc = 100 ,
ecutrho = 300 ,
occupations = 'smearing' ,
degauss = 0.005 ,
smearing = 'methfessel-paxton' ,
nspin = 2 ,
starting_magnetization(1) = 1.0,
tot_magnetization = 6.0 ,
/
&ELECTRONS
conv_thr = 1.0e-9 ,
mixing_beta = 0.7 ,I
diagonalization = 'david' ,
/
ATOMIC_SPECIES
Fe 58.69000 Fe.pbe-nd-rrkjus.UPF
ATOMIC_POSITIONS angstrom
Fe 0.000000000 0.000000000 0.000000000
Fe 2.048000000 0.000000000 0.000000000
K_POINTS automatic
1 1 1 1 1 1
======================
Giovani
2011/2/13 Duy Le <ttduyle at gmail.com>
> You should be able to fix magneticmoment of system at the desired
> value (say 6, 6.5, 7) to see which one give you the lowest energy.
> --------------------------------------------------
> Duy Le
> PhD Student
> Department of Physics
> University of Central Florida.
>
> "Men don't need hand to do things"
>
>
>
> On Sun, Feb 13, 2011 at 1:16 AM, Giovani Faccin
> <faccin.giovani at gmail.com> wrote:
> > Dear Paolo,
> >
> > Thanks for the reply.
> >
> > Just to make sure that the simulation cell size is not an issue (so that
> the
> > system is really finite), I've tested different possibilities, including
> > some quite big cells. Still, after a certain size the value of the
> > magnetization is converging to 6.82 instead of the expected 6.
> >
> > So something else is causing this. Unfortunately I've got no clue as to
> what
> > could it be.
> >
> > Should it be of any help, this is my input file:
> >
> >
> > &CONTROL
> > calculation = 'scf' ,
> > restart_mode = 'from_scratch' ,
> > wf_collect = .true. ,
> > outdir = './output' ,
> > pseudo_dir = '../pseudo/' ,
> > prefix = 'fe' ,
> > etot_conv_thr = 1.0D-9 ,
> > forc_conv_thr = 1.0D-6 ,
> > tstress = .true. ,
> > tprnfor = .true. ,
> > /
> > &SYSTEM
> > ibrav = 1,
> > celldm(1) = 43,
> > nat = 2,
> > ntyp = 1,
> > ecutwfc = 100 ,
> > ecutrho = 300 ,
> > occupations = 'smearing' ,
> > degauss = 0.02 ,
> > smearing = 'methfessel-paxton' ,
> > nspin = 2 ,
> > starting_magnetization(1) = 1.0,
> > /
> > &ELECTRONS
> > conv_thr = 1.0e-9 ,
> > mixing_beta = 0.7 ,
> > diagonalization = 'david' ,
> > /
> > ATOMIC_SPECIES
> > Fe 58.69000 Fe.pbe-nd-rrkjus.UPF
> > ATOMIC_POSITIONS angstrom
> > Fe 0.000000000 0.000000000 0.000000000
> > Fe 2.047510 0.000000000 0.000000000
> > K_POINTS automatic
> > 1 1 1 1 1 1
> >
> > Any suggestions are highly welcome.
> >
> > Giovani
> >
> >
> > 2011/2/12 Paolo Giannozzi <giannozz at democritos.it>
> >>
> >> On Feb 11, 2011, at 17:09 , Giovani Faccin wrote:
> >>
> >> > My question: shouldn't those numbers be integers?
> >>
> >> only in finite systems, if you neglect spin-orbit.
> >>
> >> P.
> >> ---
> >> Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
> >> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> >> Phone +39-0432-558216, fax +39-0432-558222
> >>
> >>
> >>
> >>
> >> _______________________________________________
> >> Pw_forum mailing list
> >> Pw_forum at pwscf.org
> >> http://www.democritos.it/mailman/listinfo/pw_forum
> >
> >
> >
> > --
> > Giovani
> >
> > _______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
> >
> >
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--
Giovani
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