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["Chun Li " <chun.li@mf.mpg.de>]

Dear Prof. Xavier and abinit users,

When I performed a SCF density computation before the band structure
calculation for ZnO, I always can not obtain the convergent result. I
tried increasing the density of the k-points mesh, increasing ecut,
increasing nstep, and rechecked the unit cell I defined, but still
cannot find where the problem is. (I used the Troullier-Martins PP for
Zn and O, respectively.)

The warning message is:
scprqt:  WARNING -
  nstep=  120 was not enough SCF cycles to converge;
  maximum energy difference=  5.243E-02 exceeds toldfe=  1.000E-10


Obviously, the result is much far from convergence now. I think
modifying the mixing parameter may work. But I don't know how to modify
it in ABINIT. That is, I don't know what the default value for the
percent of updating the electronic density during iteration
calculations, and how to control it. Do you have any ideas? 

I think another possibility is because of the PPs. So I want to modify
some parameters in the PP files. Could anyone tell me how to modify the
parameters to obtain softer, medium, and harder PPs, respectively?
Thanks a lot.

I am very sorry for my disturbing you again. But I really want to get
some useful information from you. Any advice from you will be important
for me.

Best regards.

Chun Li




My input:

# Crystalline ZnO
#
# Computation of the band structure.
# First, a SCF density computation, then a non-SCF band structure
calculation.

ndtset 2

#Dataset 1 : usual self-consistent calculation

iscf1   3
ngkpt1  48 48 32
prtden1  1         # Print the density, for use by dataset 2
toldfe1  1.0d-10

#Dataset 2 : the band structure
iscf2    -2
getden2  -1
kptopt2  -4
nband2   24
ndivk2   8 16 8 16      # 8, 16, 8 and 16 divisions of the 4 segments,
delimited
                        # by 5 points.
kptbounds2  0.0    0.0     0.0  # Gamma point
            0.0    0.0     1/2  # A point
            0.0    1/2     1/2  # H point
            0.0    1/2     0.0  # K point
            0.0    0.0     1.0  # Gamma point in another cell.
prtvol2  10
tolwfr2  1.0d-20
enunit2  1             
#######################################################################

#Definition of the unit cell
acell   6.15956186 6.15956186 9.83980322    
angdeg  90 90 120

#Definition of the atom types
ntypat 2          
znucl 30 8        

#Definition of the atoms
natom 4           # There are 4 atoms
typat 1 2 1 2
xred                 # This keyword indicate that the location of the
atoms
                     # will follow, one triplet of number for each atom
   0.0  0.0  0.0     # Triplet giving the REDUCED coordinate of atom
Zn1.
   0.0  0.0  0.3820  # Triplet giving the REDUCED coordinate of atom O1.
   1/3  2/3  1/2     # Triplet giving the REDUCED coordinate of atom
Zn2.
   1/3  2/3  0.8820  # Triplet giving the REDUCED coordinate of atom O2.
                     

#Definition of the planewave basis set
ecut   48.0         

#Definition of the SCF procedure
nstep  120           
diemac 4.5