[Pw_forum] fluctuation in SCF energies of CO adsorbed on Pd110

Axel Kohlmeyer akohlmey at gmail.com
Mon Apr 21 13:59:06 CEST 2014 

On Mon, Apr 21, 2014 at 6:28 AM, David Foster <davidfoster751 at yahoo.com> wrote:
> Thanks Axel
> Yes, in chemistry wee see always the MOs. But in many unknown cases, we should calculate the MOs by computations. To use the codes, we need to define 2S+1. In quantum chemistry codes we use different spin-multiplicity, and we choose each one that give smaller energy. What about plane-wave methods?

where in the schoedinger equation does it say it only works for
atom-centric basis sets?

> Why choosing spin-polarization causes that the energy fluctuate so much?

i think you are jumping to conclusions here. have you run the slab
configuration without the CO molecule. charge sloshing can happen for
all kinds of reasons, and usually it is affected by the amount of
mixing used and not so much by doing LSDA, but using LSDA does offer
additional degrees of freedom for the electronic system to evolve and
thus can emphasize problems like charge sloshing.

> If I compare these two calculations (one with spin-polarization and one without it), I should get the same energy. Is it right?

only if there is no magnetization.

axel.

> Thanks again
> Any help will be appreciated.
>
> Regards
>
> David Foster
>
> Ph.D. Student of Chemistry
>
> --------------------------------------------
> On Mon, 4/21/14, Axel Kohlmeyer <akohlmey at gmail.com> wrote:
>
>  Subject: Re: [Pw_forum] fluctuation in SCF energies of CO adsorbed on Pd110
>  To: "PWSCF Forum" <pw_forum at pwscf.org>
>  Date: Monday, April 21, 2014, 1:17 AM
>
>  On Mon, Apr 21, 2014 at 12:03 AM,
>  David Foster <davidfoster751 at yahoo.com>
>  wrote:
>  > Dear Yun
>  > Thanks for your rapid answer. Considering your answer,
>  I have two more questions:
>  >
>  > 1- In the system I have carbon monoxide. carbon atom
>  has 4 electron in its valance. between O and C there is a
>  triple bond. So, carbon may have one unpaired electron that
>  needs spin-polarization defined. Is it right?
>
>  wrong. electrons cannot be "assigned" to individual atoms,
>  they occupy
>  "molecular" orbitals. please help yourself to a little
>  quantum
>  chemistry refresher.
>
>  > 2- Surface of metals due to the charge density near to
>  the surface needs spin-polarization. Is it right?
>
>  wrong. you need spin polarization only if you have unpaired
>  electrons..
>
>  > One more point. I have prepared input with one
>  graphical program. When I see the input file with XCrysDen,
>  in the primitive form everything is OK, but in conventional
>  form, three to four Pd atoms in the edge of cell seems to be
>  missing!!!!
>
>  that is just visualization. probably your initial geometry
>  has some
>  rounding errors in the positions.
>
>  axel.
>
>  > Regards
>  >
>  > David Foster
>  >
>  > Ph.D. Student of Chemistry
>  >
>  > --------------------------------------------
>  > On Sun, 4/20/14, Yun Wang <yun.wang at griffith.edu.au>
>  wrote:
>  >
>  >  Subject: Re: [Pw_forum] fluctuation in SCF
>  energies of CO adsorbed on Pd110
>  >  To: "PWSCF Forum" <pw_forum at pwscf.org>
>  >  Date: Sunday, April 20, 2014, 2:41 PM
>  >
>  >  Hi David,I think
>  >  you need not consider the spin polarization for
>  this system,
>  >  which will accelerate the
>  >  convergancy.Cheers,Yun
>  >
>  >
>  >
>  >
>  >
>  >  On Mon, Apr 21, 2014
>  >  at 2:20 AM, David Foster <davidfoster751 at yahoo.com>
>  >  wrote:
>  >
>  >
>  >  Dear users
>  >
>  >
>  >
>  >  I have prepared an input for interaction between
>  CO and
>  >  Pd(110). I optimized 3*3*3 supercell of Pd bulk,
>  and then
>  >  cleaved a 110 surface and constructed a slab. I
>  inserted CO
>  >  molecule which has been optimized with QE5.0.2 in
>  it. Now, I
>  >  try to optimize this mixed system (CO+Pd(110)).
>  >
>  >
>  >
>  >
>  >
>  >  My main problem is that in scf I see the
>  fluctuation in
>  >  energies. My input and output has been attached.
>  In all
>  >  calculations I used QE5.0.2 and the same USPP. I
>  used PBE
>  >  DFT in the PP. I used nspin=2 due to the presence
>  of oxygen
>  >  atom. I introduced start_magnetization for all
>  species. I
>  >  fixed three bottom layers in the cell. I used
>  ibrav=14 to
>  >  optimize bulk phase of Pd, and didn't change it
>  in all
>  >  computation.
>  >
>  >
>  >
>  >  I used degauss=0.001RY. In addition I used
>  smearing
>  >  technique for both bulk and slab.
>  >
>  >
>  >
>  >  The run is continuing, but I think finally, I
>  will encounter
>  >  with problem.
>  >
>  >
>  >
>  >  Any idea for rapid convergence and solve the
>  issue in
>  >  fluctuation energy is appreciated.
>  >
>  >
>  >
>  >
>  >
>  >
>  >
>  >
>  >
>  >  Regards
>  >
>  >
>  >
>  >  David Foster
>  >
>  >
>  >
>  >  Ph.D. Student of Chemistry
>  >  _______________________________________________
>  >
>  >  Pw_forum mailing list
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>  >
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>  >
>  >
>  >
>  >  --
>  >
>  >  Dr. Yun Wang
>  >  Research Fellow
>  >  Centre for Clean Environment and Energy
>  >  Griffith School of Environment
>  >  Gold Coast Campus, Griffith University
>  >  QLD 4222, Australia
>  >  Tel:(61-7) 5552 8456
>  >  Fax:(61-7) 5552 8067
>  >
>  >
>  >
>  >
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>
>
>  --
>  Dr. Axel Kohlmeyer  akohlmey at gmail.com
>  http://goo.gl/1wk0
>  College of Science & Technology, Temple University,
>  Philadelphia PA, USA
>  International Centre for Theoretical Physics, Trieste.
>  Italy.
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-- 
Dr. Axel Kohlmeyer  akohlmey at gmail.com  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.

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