[gpaw-users] Ni in a box doesn't convergence and spin-polarized set-up

[Marcin Dulak]

Alvaro Vazquez-Mayagoitia wrote:
>
> Hi,
>
> I could to converge the isolated atom with the correct spin using a  
> bigger cell (12,11,10) .
>
> Now my problem is with the dimer and trimer which should have unpaired 
> electrons in the ground state.
>
http://link.aip.org/link/doi/10.1063/1.2162161 calculated small TM dimers,
including Ni, but they had access to an easy way of characterization of 
(integer) occupations of sd orbitals.
It would be nice to verify what do we get in gpaw using the method of 
integer occupations (if possible)
compared to calculating spin-polarized spherical atom with fractional 
occupancies as Ask suggests.

Marcin

> Thanks
> Alvaro
>
> On Dec 13, 2011 11:32 AM, "Nichols A. Romero" <naromero at alcf.anl.gov 
> <mailto:naromero at alcf.anl.gov>> wrote:
>
>     I think we tried at 0.10 and it didn't work.
>
>     Alvaro,
>
>     Can you play around with this script and see if you can get it to
>     converge?
>
>     Nichols A. Romero, Ph.D.
>     Argonne Leadership Computing Facility
>     Argonne National Laboratory
>     Building 240 Room 2-127
>     9700 South Cass Avenue
>     Argonne, IL 60490
>     (630) 252-3441 <tel:%28630%29%20252-3441>
>
>
>     ----- Original Message -----
>     From: "Ask Hjorth Larsen" <askhl at fysik.dtu.dk
>     <mailto:askhl at fysik.dtu.dk>>
>     To: "Alvaro Vazquez Mayagoitia" <fray.gory at gmail.com
>     <mailto:fray.gory at gmail.com>>
>     Cc: "Nichols A. Romero" <naromero at alcf.anl.gov
>     <mailto:naromero at alcf.anl.gov>>, "gpaw-users"
>     <gpaw-users at listserv.fysik.dtu.dk
>     <mailto:gpaw-users at listserv.fysik.dtu.dk>>
>     Sent: Tuesday, December 13, 2011 6:53:01 AM
>     Subject: Re: [gpaw-users] Ni in a box doesn't convergence and
>     spin-polarized set-up
>
>     Hi
>
>     On Tue, 13 Dec 2011, Alvaro Vazquez Mayagoitia wrote:
>
>     > Hi Ask,
>     >
>     > yes, Ni is a weird/tricky example, even for gaussian basis set codes
>     >
>     > I tried adding
>     >  fixmom=True
>     > and
>     >  occupations=FermiDirac(x)
>     > (with 0<x<1)
>     >
>     > and no success,
>     >
>     > Could you provide me an example, please?
>     >
>     >
>     > Thank you in advance,
>     > -Alvaro
>
>     Note that it isn't entirely trivial whether the calculation makes
>     *sense*
>     when the occupations are fractional - but I think it's the most
>     correct
>     way (given multiple "incorrect" alternatives) to deal with the
>     problem.
>
>     This works:
>
>     from ase import Atoms
>     from gpaw import GPAW, FermiDirac, PoissonSolver
>
>     system = Atoms('Ni')
>     system.center(vacuum=5.0)
>     calc = GPAW(occupations=FermiDirac(0.3), hund=True,
>                 poissonsolver=PoissonSolver(relax='GS', eps=1e-8))
>
>     system.set_calculator(calc)
>     system.get_potential_energy()
>
>
>
>     (the Poisson solver just makes it take less time)
>
>     You can probably reduce the Fermi smearing (just tested that it
>     works down
>     to 0.1).
>
>     Regards
>     Ask
>


-- 
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Marcin Dulak
Technical University of Denmark
Department of Physics
Building 307, Room 229
DK-2800 Kongens Lyngby
Denmark
Tel.: (+45) 4525 3157
Fax.: (+45) 4593 2399
email: Marcin.Dulak at fysik.dtu.dk

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