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 ?gaux en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur l'utilit? commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? 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://www.democritos.it/pipermail/pw_forum/attachments/20090313/ea4f6c17/attachment-0001.htm
