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[Prasenjit Sen <prasen@hri.res.in>]

Dear Abram:
     A quick suggestion is try using iscf=3 instead of 5. See if that
works.

   Best,
   Prasenjit Sen

On Mon, 19 Jun 2006, avanderg wrote:

> Hello All,
>
> I have been trying to optimize the geometry of a three layer Ni slab
> with a vacuum slab.  I have been unable to get this system to converge
> for the geometry optimization.  I first ran convergence tests for the
> system before geometry optimization to get reasonable values of ecut,
> the k points and tsmear.  Since I have been trying to run the geometry
> optimization I have changed many parameters but I still am having
> problems with the convergence.  The error I have been seeing is:
>
>  scfcge: WARNING -
>   Potential-based CG line minimization has trouble to converge.
>
> and
>
>   scfcge : ERROR -
>   Potential-based CG line minimization not converged after 13 restarts.
>   Action : read the eventual warnings about lack of convergence.
>   Some might be relevant. Otherwise, raise nband.
>
> Trying to take this into account (and the FAQ) I have used up to 130
> bands for the 3 Nickel atoms (which only has 10 valence electrons each)
> which seems extremely large to me.  I have also started to use
> non-defalut values of nline and nnsclo.  I have also used different
> convergence parameters using both tolvrs and toldfe as well for tolmxf.
> I have also tried using the initial locations of the atoms as the
> expected final result (from literature) and using the bulk spacing.  I
> have also used both the Broyden and CG values for ionmov.  It basically
> comes down to the fact that I have tried many things that have been
> mentioned in past forum posts for surface calculations for transition
> state metals.  These calculations also invariably take a large amount of
> computation time (days).  I would really appreciate some help.  Below I
> have included one of my most recent input files and I have also attached
> my output file since my log file is so large (scfcge is the only warning
> I am getting).
>
> Thank you
>
> Abram Van Der Geest
>
>
> --INPUT--------
> #I'm trying to get the ground stat of the Ni 111 surface
> #optimizing the surface
>
> #kpts
> kptopt   1
> kptrlatt  9  0  0
>           0  9  0
>           0  0  1
> shiftk   0.0  0.0  0.0
>
> #geo opt
> optcell 0
> tolmxf 1.0d-5
> ionmov 2
> ntime 15
>
> #metal
> occopt 4    #use first cold smearing option
> tsmear 0.003 # d electrons should have smaller tsmear
>
> nband 75
>
> #magnetized
> nsppol 2    #treat spin
> spinat 0.0 0.0 3.0   #break spin symmetry of atom 1
>        0.0 0.0 3.0   #break spin symmetry of atom 2
>        0.0 0.0 3.0   #break spin symmetry of atom 3
>
> #def of super cell
> acell 2*3.25564 9.796022881
> rprim    1.0 -1.0  0.0
>          0.0  1.0 -1.0
>          1.0  1.0  1.0
> ckprim  0
>
> #def of atom type
> ntypat 1   #one type of atom
> znucl 28   #and it is Ni
> natom  3   #number of atoms per supercell
> typat  3*1  #the first three atoms are nickel
>
> xred 1/3 2/3 0.78065362  #the 1st atom is at origin
>      2/3 1/3 0.0  #location of second atom
>      1.0 1.0 0.21934638  #location of atom 3
>
> #Misc
> toldfe 1.0d-5  #scf tolerance (total E)
> prtwfk  1
> getwfk -1      #get wfk from earlier run
> ixc    1       #LDA approx
> diemac 1.0d6   #preconditioner for a metal
> nstep  100      #max number of scf cycles
> ecut   25      #energy cut off for plane waves
> diemix 0.05
>
> nline  6
> nnsclo 3
>
>