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[<venomdi2000@yahoo.com>]

Good abinit user

I want to ask about two things according to the calculation of GaAs. They are
about definition of k-points grid and optimization of lattice parameter.

About definition of k-points, I want to know how to do this for zinc blende
structure like GaAs. In abinit tutorial, I only see the explanation for fcc 
and
bcc structure about their nshiftk and shiftk parameter value. 

About optimization of lattice parameter, I want to know how to give the right
value for each parameter, like optcell or ionmov. I got suggestion to use
optcell=2 for zinc blende structure, but I want to know why

This is my code
------------------------------------------------------------------------------
ndtset 5

#Optimization of the lattice parameters
optcell 2
ionmov  3
ntime  10
dilatmx 1.05
ecutsm  0.5

#Definition of the k-point grids
kptopt 1          # Option for the automatic generation of k points, taking
                  # into account the symmetry
nshiftk 1         # of the reciprocal space (that form a BCC lattice !),
                  # repeated four times, with different shifts :
shiftk 0.5 0.5 0.5

ngkpt1  2 2 2     # Definition of the different grids
ngkpt2  4 4 4
ngkpt3  6 6 6
ngkpt4  8 8 8     
ngkpt5  10 10 10 
getwfk -1         

#Definition of the unit cell and ecut, 
#for which one will have to make a convergence study
acell 3*10.18          
rprim  0.0  0.5  0.5   
       0.5  0.0  0.5   
       0.5  0.5  0.0 

#Definition of the atom types
ntypat 2          
znucl 31 33           

#First dataset : find the optimal bond length of H2, and associated total
energy
   natom  2             # There are two atoms 
   typat 1 2          
   xred   0.00 0.00 0.00
          0.25 0.25 0.25
           
#Definition of the planewave basis set
ecut  12.0         # Maximal kinetic energy cut-off, in Hartree


#Definition of the SCF procedure
nstep 10         # Maximal number of SCF cycles
toldfe 1.0d-6    
diemac 12.0      
  
---------------------------------------------------------------------------------
Thank you very much for the attention. I hope you can give me some corrections
and suggestions

With regard

Andika A.