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

[Alvaro Vazquez-Mayagoitia]

On Fri, Dec 16, 2011 at 1:03 PM, Marcin Dulak <Marcin.Dulak at fysik.dtu.dk> wrote:
> 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

The binding energy I got for Ni2 (Magmom=+2.00) is 62.3 kcal/mol and
a optimized distance of 210.1 pm,  (w fractional occupation strategy)
I think these are good numbers
Comparing with the paper that Marcin shared, the authors got 62.3
kcal/mol and 211.9 pm, with
the same multiplicity as GPAW got

-Alvaro

>
>> 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
>>
>
>
> --
> ***********************************
>
> 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
>
> ***********************************
>



-- 
-Alvaro

http://www.alcf.anl.gov/~vama/