[Pw_forum] RE : RE : A question on atomic magnetic moments
Giovani Faccin
faccin.giovani at gmail.com
Tue Feb 15 18:42:10 CET 2011
Dear Cyrille,
I recalculated the dimer with different values of nbnd. Now some interesting
changes appeared:
Value of nbnd | Magnetization
10 4.00
12 6.88
14 6.49
16 6.49
18 6.49
20 6.49
22 6.88
24 6.88
26 6.49
28 6.49
Also we dimer is now no longer at the equilibrium position; taking for
example for nbnd=20:
Forces acting on atoms (Ry/au):
atom 1 type 1 force = 0.02342880 0.00000000 0.00000000
atom 2 type 1 force = -0.02342880 0.00000000 0.00000000
For the record, the smearing contribution on these calculations goes like
this : smearing contrib. (-TS) = -0.00101846 Ry
which were made using degauss = 0.005, with 'methfessel-paxton' smearing
type.
So looks like there are two things to improve: reduce the smearing
contribution and also use a high nbnd. Peharps those high values of
magnetization at nbnd=22, 24 could be due to smearing?
I'll test it and report back on the list.
Any other suggestions, just say it, I'll give it a try.
Thanks,
Giovani Faccin
2011/2/14 BARRETEAU Cyrille <cyrille.barreteau at cea.fr>
> Dear Giovani
>
> I personnaly did calculations on Fe clusters some time ago. I always found
> "almost integer" magnetic moments.
> However I once encoutered some difficulties with the default value of
> "nbnd". I had to increase it. Try to set nbnd=20 for example...
>
> Magnetic clusters can be very tricky.. It also very common to find several
> magnetic solutions..
>
> good luck
>
> cyrille
>
> ==================================================================
> Cyrille Barreteau
> phone : +33 (0)1 69 08 29 51
> CEA Saclay fax
> : +33 (0)1 69 08 84 46
> IRAMIS, SPCSI, Batiment 462 email
> cyrille.barreteau at cea.fr
> 91191 Gif sur Yvette Cedex
> FRANCE
> ~~~~~~~~~~~~~~~~~~~~~~~~
> Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/
> ==================================================================
>
> ________________________________
>
> De: pw_forum-bounces at pwscf.org de la part de Giovani Faccin
> Date: lun. 14/02/2011 05:50
> À: PWSCF Forum
> Objet : Re: [Pw_forum] RE : A question on atomic magnetic moments
>
>
> Dear Cyrille,
>
> First of all, thanks for the reply on my post.
>
> Following your suggestion, I've run a few calculations with lower degauss
> values. In particular, the ones reported on the message for Duy Le were made
> with a much smaller value ( 0.005 ) than the original 0.02 from the first
> message. Besides that, I've tried degauss values as low as 0.002 without any
> significant improvement on the final magnetization.
>
> I'm still wondering how do people find 6.00 so easily for the
> magnetization. I'm trying with 2 different DFT codes and no way I'm reaching
> those results, even though bulk/dimer equilibrium distances and force
> constants appear to be ok.
>
> Any other ideas, just tell me, I'll try it and report back on the list.
>
> Thanks again,
>
> Giovani
>
>
>
> 2011/2/13 BARRETEAU Cyrille <cyrille.barreteau at cea.fr>
>
>
> Dear Giovani
> Try to decrease the degauss value of your smearing.. and see what
> happens.
>
> cyrille
>
>
> ==================================================================
> Cyrille Barreteau
> phone : +33 (0)1 69 08 29 51
> CEA Saclay
> fax : +33 (0)1 69 08 84 46
> IRAMIS, SPCSI, Batiment 462 email
> cyrille.barreteau at cea.fr
> 91191 Gif sur Yvette Cedex
> FRANCE
> ~~~~~~~~~~~~~~~~~~~~~~~~
> Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/
> ==================================================================
>
> ________________________________
>
> De: pw_forum-bounces at pwscf.org de la part de Giovani Faccin
> Date: dim. 13/02/2011 07:16
> À: PWSCF Forum
> Objet : Re: [Pw_forum] A question on atomic magnetic moments
>
>
> 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
>
>
>
>
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