The ABINIT Users Mailing List ( CLOSED )

["Anglade Pierre-Matthieu" <anglade@gmail.com>]

PS: P. Boulanger and I suggest that you force nsym to 1  in order to
have a chance to get an amorphous state.

On 5/2/07, Anglade Pierre-Matthieu <anglade@gmail.com> wrote:
> Hello fet,
>
> From your input we guess that you are trying to get amorphous
> materials from a really out of equilibrium structure. I've discussed
> with P. Boulanger about your file and here are a few comments:
>
> 1) getwfk -1 is not usefull here since you expect all your
> configuration to lead to very different amorphous state. At best this
> makes your calculations longer.
>
> 2) Hopefully we interpret your starting acell, for your four datasets,
> correctly. Otherwise we really wonder what they are intended to. We
> think that you expect quite different relaxations under different
> pressures.
>
> 3) your ecut looks small for a cell with oxygen. By contrast your k
> point mesh looks terribly converged. Even for the smallest cell and
> not mentioning the 3 next where it is going to be much worst than a
> waste of computation time. You may want to find an equilibrium between
> k-mesh convergence and ecut convergence.
>
> 4) It looks like your starting configuration are much too far from
> equilibrium for CG to converge. You may better try to start with
> something like "ionmov 7", get semi relaxed atmic position then
> continue with ionmov 3.
>
> Regards
>
> PMA
>
>
> On 5/2/07, fet@iisb.fraunhofer.de <fet@iisb.fraunhofer.de> wrote:
> > Hi,
> >
> > Here is a copy of my input file for the calculation on amorphous
> > silicon. The forces just don't converge any help is appreciated. I keep
> > getting the following warning
> >
> > fconv : WARNING -
> >   ntime=   25 was not enough Broyd/MD steps to converge gradients:
> >   max grad (force/stress) = 1.6705E+02 > tolmxf= 5.0000E-04 ha/bohr
> > (free atoms)
> >
> >
> > Thanks
> >
> > #ABINIT input file to calculate electronic structure of bulk
> > # amorphous Silicon dioxide
> > #
> >
> > #prtden   1             #print the electron density
> > #prtdos   2             #print the LDOS
> > #prteig   1             #print the eigenenergies
> > enunit   1             #output energies in electron volts
> > getwfk  -1
> >
> > ndtset   4             #two data sets: one crystalline one amorphous
> > udtset   1 4
> > #-----------------------------------------------------------------------
> > #first data set defining crystalline SiO2 with FCC lattice structure and
> > 6 atom basis
> >
> > #define cell dimensions
> > acell?:    10.217 10.217 10.217 acell?+ 5.0 5.0 5.0
> > rprim    0.5 0.5 0.0   #define FCC lattice for SiO2
> >          0.0 0.5 0.5
> >          0.5 0.0 0.5
> >
> > #chkprim  0            #allow the usage of a non-primitive cell:
> >
> > #define the atoms
> > natom    6            #6 atoms per unit cell
> > ntypat   2            #two types of atoms
> > znucl    14 8         # atoms with atomic numbers 14 for silicon and 8
> > for oxygen
> > typat    2*1 4*2      #2 silicon atoms and 4 oxygen atoms
> > xred
> >          3*0.0
> >          3*0.25
> >          3*0.125
> >          1/4 1/8 1/4
> >          1/8 1/4 1/4
> >          3/8 3/8 3/8
> > #---------------------------------------------------------------------------
> >
> > #Exchange-correlation functional
> > ixc     11           #GGA perdew-burke-ernzerhof functional
> >
> >
> > #Definition of the planewave basis set
> > ecut1?    14.0
> >
> >
> > #Definition of the SCF procedure
> > nstep   20          # Maximal number of SCF cycles
> > toldff  5.0d-5
> >
> > #diemac  12.0       # Although this is not mandatory, it is worth to
> > iprcell  45         # 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 prescription for bulk silicon.
> >
> >
> > #Definition of the k-point grid
> > kptopt    1         # Option for the automatic generation of k points,
> > taking
> >                     # into account the symmetry
> > ngkpt     8 8 8
> > nshiftk   4
> > shiftk    0.5 0.0 0.0
> >           0.0 0.5 0.0
> >           0.0 0.0 0.5
> >           0.5 0.5 0.5
> >
> > #Optimization of the lattice parameters
> > ionmov  3
> > ntime   25
> > tolmxf  5.0d-4
> >
> > #dilatmx 1.05
> > #ecutsm  0.5
> >
> >
> > Anglade Pierre-Matthieu schrieb:
> > > > Hi,
> > > >
> > > > For us to be able to help you efficiently you should send us your
> > > > input and output file. Many configuration problems can prevent
> > > > convergency of a calculation
> > > > (http://www.abinit.org/about/?text=../Infos/netiquette).
> > > >
> > > > If you have made any error in your input it is natural that your
> > > > calculation do not converge :
> > > > not enough bands, atoms misplaced, bad estimation of your static
> > > > macroscopic permittivity (diemac) ...
> > > >
> > > > If all the above is correct, you may try to use "iprcel".
> > > >
> > > > regards
> > > >
> > > > PMA
> > > >
> > > >
> > > > On 4/27/07, Chol-Jun Yu <yucj@ghi.rwth-aachen.de> wrote:
> > >> >> Hello,
> > >> >>
> > >> >> you can cited the following reference: Phys. Rev. Lett. 97,
> > >> >> 066101(2006).
> > >> >>
> > >> >> Cheers.
> > >> >>
> > >> >> On Friday, 27. April 2007 13:01, fet@iisb.fraunhofer.de wrote:
> > >>> >> > Hello Abinites,
> > >>> >> >
> > >>> >> > Has anybody tried to model amorphous materials and defects with a
> > >> >> supercell
> > >>> >> > before. I tried for a 10 layer supercell of Silicon dioxide ... it
> > >> >> just
> > >>> >> > does not seem to converge.
> > >>> >> >
> > >>> >> > Any help??
> > >> >>
> > >> >>
> > >> >> Yu Chol Jun
> > >> >> 
> -----------------------------------------------------------------------------
> > >> >>
> > >> >> Computational Materials Engineering(CME)
> > >> >> Center for Computational Engineering Science(CCES)
> > >> >> Institute of Mineral Engineering(GHI), RWTH Aachen
> > >> >> Mauerstrasse 5, D-52064 Aachen, Germany
> > >> >> Tel: ++49 241 80 94969
> > >> >> Fax: ++49 241 80 92271
> > >> >> e-mail: yucj@ghi.rwth-aachen.de
> > >> >> 
> -----------------------------------------------------------------------------
> > >> >>
> > >> >>
> > >> >>
> > > >
> > > >
> >
>
>
> --
> Pierre-Matthieu Anglade


--
Pierre-Matthieu Anglade