[Pw_forum] roblem with bfgs algorithm optimizer for spin polarized system
pc229 at kent.ac.uk
pc229 at kent.ac.uk
Fri Mar 13 15:07:22 CET 2009
Thanks for the reply,
buT I am still thinking that should be a bug in the optimizer, since I also tried to run my system like a metal and nothing gonna change.
If I change the optimization method I can reach easly the convergence.
Cheers, Piero
----- Original Message -----
From: Giuseppe Mattioli <giuseppe.mattioli at mlib.ism.cnr.it>
Date: Friday, March 13, 2009 11:21 am
Subject: Re: [Pw_forum] roblem with bfgs algorithm optimizer for spin polarized system
To: PWSCF Forum <pw_forum at pwscf.org>
>
> Dear Piero
>
> > &ELECTRONS
> > /
> The default beta mixing parameter is often too high to fit for
> many purposes.
> Try to use the keyword mixing_beta = 0.3 (e.g.) within the
> &electrons group.
>
> > occupations = 'fixed' ,
> This is not a good choice (at least in my experience) when you
> deal with
> system in which the magnetization may change. Try to add a
> gaussian or a cold
> smearing.
>
> Yours
>
> Giuseppe
>
> On Friday 13 March 2009 01:23:46 pc229 at kent.ac.uk wrote:
>
> > Dear PWscf developers,
> > I am trying to optimize, on the latest version of the
> espresso code
> > (v4.0.4 ), the cell parameter and also the ionic coordinate
> of hematite.
> > Initially I treat hematite like an insulator using the following
> > pseudo-potential :Fe.pbe-sp-van_ak.UPF for Iron and O.pbe-
> van_ak.UPF for
> > oxygen (I attached the input at the bottom). To optimize both
> atomic> coordinates and cell parameters I used bfgs algorithm .
> As you know
> > hematite is an open-shell system, and you need to define the spin
> > orientation in order to describe it like a ferro-magnetic or
> > anti-ferromagnetic system. I choose the anti-ferromagnetic
> one, that means
> > to have the total magnetization equal to 0 every SCF cycle
> and absolute
> > magnetization ranging from 11-16 (this highly pseudo potential
> dependent).> Anyway, for the first SCF cycle the magnetization
> carried out is correct,
> > while after the first geometry optimization step hematite
> starts to lose
> > the spin and the energy also dancing between two value not
> allowing the
> > SCF to converge. So attempting to managed this problem I try
> to run it like
> > a metal introducing a methfessel-paxton smearing. Nothing
> seems to
> > change, the SCF of the second optimization step doesn't
> converge as
> > previously. Then I tried to restart my calculation from the
> first point
> > coordinates and the first SCF step converged, whilst the next
> no as in the
> > previous cases . This is very strange and get me frustrated !
> Then I run
> > the same calculation changing both optimization algorithm to
> damp for the
> > ionic coordinate and damp-w for the cell. In this way the SCFs
> after the
> > first optimization cycle seem to converge with the right
> magnetization and
> > the next as well. I did also a further trial, because I need
> to use the
> > bfgs algorithm to optimize my structure. I tried to run the
> same system on
> > a previous version of espresso (v.2.1.2), and treating it like
> a metal
> > (with methfessel-paxton smering) and using bfgs for ionic
> coordinate and
> > damp for cell optimization (since bfgs wasn't implemented to
> optimize the
> > cell parameter in this version) the first SCF reached the
> convergence and
> > the following as well. How can I solve it ? I also read in
> the documents
> > related to PWscf that bfgs for optimizing cell parameters (vc-
> relax) is
> > still in a experimental version. Would it be possible that It
> has some
> > problem with spin polarized systems?? How can I manage this
> problem? I need
> > desperately to use bfgs to optimize the hematite.
> >
> >
> > Best Regards, Piero
> >
> >
> > &CONTROL
> > title = 'opt_bulk_PBE_van3.inp' ,
> > calculation = 'vc-relax' ,
> > restart_mode = 'from_scratch' ,
> > wf_collect = .true. ,
> > outdir =
> >
> '/home/pc229/backup/Counts/PWscf/Fe2O3_bulk/PWSCF/Fe2O3_bulk/opt_bulk_PBE_v>an/' , pseudo_dir =
> >
> '/home/pc229/backup/Counts/PWscf/Fe2O3_bulk/PWSCF/Fe2O3_bulk/pseudo/' ,
> > prefix = 'opt_bulk_PBE_van3.inp' ,
> > /
> > &SYSTEM
> > ibrav = 5,
> > celldm(1) = 11.091428,
> > celldm(4) = 0.587237106,
> > nat = 10,
> > ntyp = 3,
> > ecutwfc = 50 ,
> > nosym = .true. ,
> > nbnd = 70,
> > nelec = 100,
> > tot_charge = 0.000000,
> > occupations = 'fixed' ,
> > nspin = 2 ,
> > starting_magnetization(1) = 1.,
> > starting_magnetization(2) = -1.,
> > starting_magnetization(3) = 0.,
> > tot_magnetization = 0 ,
> > /
> > &ELECTRONS
> > /
> > &IONS
> > ion_dynamics = 'bfgs' ,
> > /
> > &CELL
> > cell_dynamics = 'bfgs' ,
> > wmass = 2001.0060 ,
> > cell_dofree = 'all' ,
> > /
> > ATOMIC_SPECIES
> > Fe 55.62000 Fe.pbe-sp-van_ak.UPF
> > Fe1 55.62000 Fe.pbe-sp-van_ak.UPF
> > O 15.99000 O.pbe-van_ak.UPF
> > ATOMIC_POSITIONS crystal
> > Fe 0.144358141 0.144342247 0.144393006
> > Fe1 0.355605889 0.355642696 0.355656118
> > Fe1 0.644394003 0.644359012 0.644344959
> > Fe 0.855641399 0.855655859 0.855605070
> > O 0.556470421 0.943529173 0.250007053
> > O 0.250006034 0.556470770 0.943529639
> > O 0.943529367 0.250006711 0.556470944
> > O 0.443532949 0.056467967 0.749992942
> > O 0.749994148 0.443532454 0.056467520
> > O 0.056467649 0.749993110 0.443532750
> > K_POINTS automatic
> > 4 4 4 0 0 0
> >
> >
> > --
> > Pieremanuele Canepa
> > Room 230
> > School of Physical Science
> > Ingram Building
> > University of Kent,
> > Canterbury,
> > Kent, CT2 7NH
> > United Kingdom
> > Cell: +44-7768685833
> > ID Skype: pieremanuele
> > ID msn: pieremanuele83 at hotmail.com
> > --------------------------------------------------------
>
> --
> ********************************************************
> - Article premier - Les hommes naissent et demeurent
> libres et ègaux en droits. Les distinctions sociales
> ne peuvent être fondèes que sur l'utilitè commune
> - Article 2 - Le but de toute association politique
> est la conservation des droits naturels et
> imprescriptibles de l'homme. Ces droits sont la libertè,
> la propriètè, la sùretè et la rèsistance à l'oppression.
> ********************************************************
>
> Giuseppe
> Mattioli
> CNR - ISTITUTO DI STRUTTURA DELLA
> MATERIA
> v. Salaria Km 29,300 - C.P.
> 10
> I 00016 - Monterotondo Stazione
> (RM)
> Tel + 39 06 90672836 - Fax +39 06
> 90672316
> E-mail: <giuseppe.mattioli at ism.cnr.it>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20090313/8f287951/attachment.html>
More information about the users
mailing list