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[matthieu verstraete <matthieu.jean.verstraete@gmail.com>]

your cutoff is huge - you should find softer pseudopotentials, and
converge the box size more systematically, starting with a small one
and looking at different quantites as a function of acell. You may
even have to go to bigger boxes to converge properly.

Also consider using icoulomb for boundary conditions in the Poisson
solver (places constraints on the box shape and pseudopotentials,
though).

Matthieu

On Thu, Apr 2, 2009 at 2:27 PM,  <cszakacs@mun.ca> wrote:
> Dear users,
>
> I am testing some zero-dimensional calculations with Abinit. I am following 
> the
> example given in Lesson 1 (with the hydrogen).
> I want to optimize a ZnO cluster containing 12 atoms in a supercell (I am
> considering it to be neutral). Here is my input:
>
> acell 30 30 30
> ecut 80
> #optimization
> natom 12
> ionmov 3             # Use the modified Broyden algorithm
> ntime 10            # Maximum number of Broyden "timesteps"
> tolmxf 5.0d-4        # Stopping criterion for the geometry optimization : 
> when
>                         # the residual forces are less than tolmxf, the
> Broyden
>                         # algorithm can stop
> xangst           1.69555300   -0.71202600   -1.53300200
>                 -0.23112400    1.82435000   -1.53300200
>                 -1.46439400   -1.11236700   -1.53302300
>                  0.23532700   -1.75354400   -0.85437000
>                  0.23971200   -1.71537200    1.06255400
>                 -1.63626200    0.67295000   -0.85436900
>                 -1.60538200    0.65003600    1.06257500
>                  1.40092400    1.08057300   -0.85436500
>                  1.36569300    1.06523600    1.06259300
>                  1.76646300   -0.70453700    1.71357600
>                 -1.49337800   -1.17754600    1.71354300
>                 -0.27303100    1.88202800    1.71359200
>
>
>
> toldff 5.0d-5        # Will stop the SCF cycle when, twice in a row,
>                         # the difference between two consecutive evaluations
> of
>                         # forces differ by less than toldff (in 
> Hartree/Bohr)
> nband  108            #  band for energy calc
> #Definition of the atom types
> ntypat 2          # There is only one type of atom
> znucl 8 30           # The keyword "znucl" refers to the atomic number of 
> the
>                  # possible type(s) of atom. The pseudopotential(s)
>                  # mentioned in the "files" file must correspond
>                  # to the type(s) of atom. Here, the only type is Hydrogen.
>
>
> #Definition of the atoms
> typat 1 1 1 2 1 2 1 2 1 2 2 2        # For the first dataset, both numbers 
> will
> be read,
>                  # while for the second dataset, only one number will be 
> read
>
> #Definition of the k-point grid
> nkpt 1            # Only one k point is needed for isolated system,
>                  # taken by default to be 0.0 0.0 0.0
>
> #Definition of the SCF procedure
> iprcel 45
> nstep 10          # Maximal number of SCF cycles
> #toldfe is no more defined, as toldff is used above...
> diemac 2.0        # Although this is not mandatory, it is worth to
>                  # precondition the SCF cycle. The model dielectric
>                  # function used as the standard preconditioner
>                  # is described in the "dielng" input variable section.
>                  # Here, we follow the prescriptions for molecules
>                  # in a big box
>
> The main problem I am encountering is the huge memory needed and the length 
> of
> the computation (about 8GB memory and the calculation is runnning now for a 
> few
> days and it didn't finished yet.)
>
> Is this normal? Or I am using a too large ecut?
> I have done before some calculation on the bulk ZnO and using 80 as the 
> value
> for the ecut I've got good convergence, so I considered that this would be 
> ok.
> Or are there other things that I've missed?
> Or the acell parameters are to high?
>
> Could you give me some advice about this?
>
> Thank you,
>
> Csaba Szakacs
>
>
>
>



-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Matthieu Verstraete

European Theoretical Spectroscopy Facility (ETSF)
Dpto. Fisica de Materiales,
U. del Pais Vasco,
Centro Joxe Mari Korta, Av. de Tolosa, 72,   Phone: +34-943018393
E-20018 Donostia-San Sebastian, Spain        Fax  : +34-943018390

Mail : matthieu.jean.verstraete@gmail.com
http://www-users.york.ac.uk/~mjv500