The ABINIT Users Mailing List ( CLOSED )

[fet@iisb.fraunhofer.de]

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
>> >> -----------------------------------------------------------------------------
>> >>  
>> >>
>> >>
>> >>
> >
> >