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

Dear all,

 

When I tried to calculate the band structure of ZnO, I found that the first step (a SCF density computation) did not converge when I set nstep=80, but the second step (a non-SCF band structure calculation) converged. However, because the density data used in the second step are derived from the first step, so the results could not be reliable. So I tried increasing the value of nstep, but after that, the following error massage lines are appeared in the end of the log file:

 

scfcge : ERROR -

  Potential-based CG line minimization not converged after 13 restarts.

  Action : read the eventual warnings about lack of convergence.

  Some might be relevant. Otherwise, raise nband.

 

 leave_new : decision taken to exit ...

FORTRAN STOP  1

 

But when I tried to raise the nband, the same error message still appeared. I really don’t know how to modify the input file then. Can you give me some suggestions? Thanks a lot. (I copied the input file below)

 

Best regards.

 

Chun Li

 

 

My input file:

# 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

 

ngkpt1  3 3 2

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        

acell   6.15956186 6.15956186 9.83980322    

angdeg  90 90 120

ntypat 2         

znucl 30 8       

natom 4          

typat 1 2 1 2

xred                

   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   32.0        

#Definition of the SCF procedure

nstep  100       # Maximal number of SCF cycles

diemac 9.0