The ABINIT Users Mailing List ( CLOSED )

[cszakacs@mun.ca]

Hello,

I have used a lower cutoff, but now I am encountering another problem. Even
though it didn't fully converged yet, I am detecting some strange things, it
seems the cluster explodes....the Zn and O atoms are flying all around the
box...it is a mess. 
(I have optimized the same cluster using other software (Gaussian) at HF level
of theory with no problem, but if I want to tackle significantly larger
clusters it will be a problem, that is why I am testing the optimization  with
Abinit.)
The input file it is the same, as in my earlier email, I've changed the ecut 
and
I am using the TM pseudopotentials. 
Any suggestions? 
Or I would appreciate any directions to an article or some literature which
deals with ZnO clusters using Abinit. 
I've looked around and I didn't find any yet.

Thanks,

Csaba


Quoting 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
> 
> 


-- 
Csaba Szakacs
PhD Candidate
Memorial University
Dept. of Chemistry
St. John's, NL
Tel.: 737-6118