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[<venomdi2000@yahoo.com>]

good night abinit user..

For now, I am doing simulation about atom bridge of Fe which has twisted 
ladder
structure. I am doing two kinds of simulation: with nsppol=1 and with 
nsppol=2.
Later, I intend to compress my structure and see the value of etotal and
magnetic moments. I provide my code below. My problems are, that I have no 
idea
of the value which I will give to iscf parameter. Please give me suggestion
about the choice of iscf value which I will give..

My another problem is about determining value of tsmear. How to do convergence
est with tsmear. I ever did convergence test with this parameter with respect
to etotal, and found that i went divergent...

The following is my input file



# chain of iron : computation of the total energy
#

ndtset 2  
#Definition of the unit cell
acell 2.2 10 10    # The keyword "acell" refers to the
                  # lengths of the primitive vectors (in Bohr)

spinat2   0.0 0.0 4.0
         0.0 0.0 4.0
         0.0 0.0 4.0
         0.0 0.0 4.0
 nsppol2   2
prtdos 1
occopt 3
nband 24
 tsmear 0.12    
prtden 1
      

#Definition of the atom types
ntypat 1          # There is only one type of atom
znucl 26          # 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 iron.
                         

#Definition of the atoms
natom 4           
typat 1 1 1 1      
xcart                     
   0.0   1.3  0.0  
   0.0  -1.3  0.0
   2.55  0.0  1.3  
   2.55  0.0 -1.3     
    

#Definition of the planewave basis set
 ecut 24             # Maximal kinetic energy cut-off, in Hartree


#Definition of the k-point grid
kptopt 1          # Option for the automatic generation of k points, taking
                  # into account the symmetry
ngkpt  4 4 4     # Definition of the different grids
nshiftk 1
 

#Definition of the SCF procedure
nstep 15          # Maximal number of SCF cycles
toldfe 1.0d-6     # Will stop when, twice in a row, the difference 
                  # between two consecutive evaluations of total energy 
                  # differ by less than toldfe (in Hartree) 
diemac 12.0       # 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 prescription for bulk silicon.