[Wien] Problems with PORT minimization!

[Timo Jacob]

> The "***false convergence***" means that the algorithm could not find a
> location with a better energy consistent with the forces that you are
> giving it. This may not be an issue, since the numerical accuracy of
> the energies and forces in Wien is limited. Unfortunately you don't
> provide all the information that is needed to diagnose your problem:
> 	1) Are your energies/charges etc well converged?
Yes, they are well converged. Before running mini I always perform a full SCF 
run with -cc 0.0001. After that I calculate the forces with the propriate 
corrections.
>	2) Is it a CXZ spacegroup (in which case there are other problems)
It is a hexagonal surface unitcell, Pt(111).
>
> Beyond this, there is a basic point. You have fixed the positions of your
> central Pt atoms, so it is quite reasonable that the forces do not go to
> zero at the (constrained) energy minimum.
Since there is only a single atom in each layer (1x1 surface unit cell), this 
should not affect. Besides an avoided translation (in z-direction) of the 
entire slab, the system should be able to achieve his global minimum. The 
only real constraint is given by the symmetry, which fixes the x and y 
coordinates. Thus, I only checked the z-components of the force-vectors.

Thanks,
Timo.

>
> On Mon, 18 Oct 2004, Timo Jacob wrote:
> > Hello,
> >
> > I try to otimize the structure of a 5 layer slab (1x1)  including 3
> > central Pt layers and an oxygen layer at each surface.
> > For my calculations I use an energy cutoff of 15 Ry (for an initial
> > structure optimization) and the central Pt layer is fixed during the
> > geometry optimization.
> > Using the PORT option with the *.inM input attached below,
> > the total energy mostly decreases but the forces seem to converge to
> > finite numbers
> >
> > :FOR002 -38.535
> > :FOR003  16.344
> >
> > and after 3-4 geometry iterations with same forces the geometry
> > optimization stops with stop_forces_small. However, *.outputM contains
> > the line ****false convergence*****.
> >
> > Any suggestions?
> >
> > Thanks in advance.
> >
> > ------------- *.inM -------------
> > PORT 2.0
> > 0 0 0 1.0
> > 1.0 1.0 1.0 1.0
> > 1.0 1.0 1.0 1.0
> > ----------------------------------
> >
> > ------------ *.in1 ---------------
> > WFFIL        (WFPRI, SUPWF)
> >   3.900000   10    4 (R-MT*K-MAX; MAX L IN WF, V-NMT
> >  -.22515   6   0      global e-param with N other choices, napw
> >  0   -0.407     0.000 CONT 1
> >  1   -0.226     0.000 CONT 1
> >  1   -3.803     0.000 CONT 1
> >  2   -0.167     0.000 CONT 1
> >  3   -0.176     0.000 CONT 1
> >  3   -4.858     0.000 CONT 1
> >  -.22515   7   0      global e-param with N other choices, napw
> >  0   -0.452     0.000 CONT 1
> >  1   -0.283     0.000 CONT 1
> >  1   -3.872     0.000 CONT 1
> >  2   -0.240     0.000 CONT 1
> >  2   -1.471     0.000 CONT 1
> >  3   -0.212     0.000 CONT 1
> >  3   -4.930     0.000 CONT 1
> >  -.22515   3   0      global e-param with N other choices, napw
> >  0   -0.367     0.000 CONT 1
> >  0   -1.468     0.000 CONT 1
> >  1   -0.292     0.000 CONT 1
> > K-VECTORS FROM UNIT:4   -9.0       2.5      emin/emax window
> > ----------------------------------
> >
> >
> > --
> > Dr. Timo Jacob                       Phone : ++49-30-8413 4816
> > Fritz-Haber-Institut                   Fax   : ++49-30-8413 4701
> >     der Max-Planck-Gesellschaft
> > Faradayweg 4-6                      e-mail: jacob at fhi-berlin.mpg.de
> > D-14 195 Berlin-Dahlem           Germany
> > ----------------------------------------------------------------------
> >               WWW: http://www.fhi-berlin.mpg.de/th/th.html
> >
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> > Wien at zeus.theochem.tuwien.ac.at
> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
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-- 
Dr. Timo Jacob                       Phone : ++49-30-8413 4816
Fritz-Haber-Institut                   Fax   : ++49-30-8413 4701
    der Max-Planck-Gesellschaft
Faradayweg 4-6                      e-mail: jacob at fhi-berlin.mpg.de
D-14 195 Berlin-Dahlem           Germany
----------------------------------------------------------------------
              WWW: http://www.fhi-berlin.mpg.de/th/th.html