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[Fabien Bruneval <fabien.bruneval@cea.fr>]

Dear Sophie,
This is not related to the GW calculation, but rather to the SCF cycles 
in the DFT part.
Neither your input file nor your output file are complete, so it is 
difficult to help you.
Before doing a GW calculation, you should be sure to be able to perform 
a "normal" DFT calculation for your particular system.
Good luck.

Fabien


us_sophie.green@yahoo.com wrote:
> Dear all,
>
> I am beening troubled with some mistakes in GW calculation. The follows is
> mistake and warning message in the log file:
>
> scfcge: WARNING -
>   Potential-based CG line minimization has trouble to converge.
>   The algorithm is restarted with more secure parameters.
>  scfcge: actual    20-9-1   1.5928E-01 -4.654626213488E+00  1.5508E-13
>  scfcge: predict           -1.1244E+00 restart the algorithm
>  scfcge:
>  scfcge: start    20-10-0   0.0000E+00 -4.654626213488E+00  1.5508E-13
>
>
> 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.
>
> #############################################
> I have increased the nband in the input file, but the error message still
> appeared.
>
> The input file is as follows:
>
> ndtset      4
> kptopt   1            # Option for the automatic generation of k points
> ngkpt    12 12 12        # Density of k points
>
> nkpt1    468
> nshiftk1  1
> shiftk1  0.5 0.5 0.5  # This grid is the most economical
> prtden1  1         # Print out dens
>
> nkpt2  468
> nshiftk2  1
> shiftk2  0.5 0.5 0.5  # This grid is the most economical
> istwfk2  468*1
> iscf2    -2             # Non self-consistent calculation
> getden2  -1             # Read previous density file
> nband2   13
> nbandkss2  100        # Number of bands to store in KSS file
>
> # Dataset3: Calculation of the screening (epsilon^-1 matrix)
> optdriver3  3        # Screening calculation
> getkss3     -1       # Obtain KSS file from previous dataset
> nband3      100       # Bands to be used in the screening calculation
> ecutwfn3    40.0      # Planewaves to be used to represent the wavefunctions
> ecuteps3    40.0      # Dimension of the screening matrix
> #ppmfrq3    16.7 eV  # Imaginary frequency where to calculate the screening
>
> # Dataset4: Calculation of the Self-Energy matrix elements (GW corrections)
> optdriver4  4        # Self-Energy
> getkss4     -2       # Obtain KSS file from dataset 1
> getscr4     -1       # Obtain SCR file from previous dataset
> nband4      25      # Bands to be used in the Self-Energy calculation
> ecutwfn4    35.0      # Planewaves to be used to represent the wavefunctions
> ecutsigx4    30.0      # Dimension of the G sum in Sigma_x
>                      # (the dimension in Sigma_c is controlled by npweps)
> nkptgw4      1                # number of k-point where to calculate the GW
> correction
> kptgw4                       # k-points
>     0.25   0.25    0.25
> bdgw4	    6  7	     # calculate 
> ecut 70.0	   # Maximal kinetic energy cut-off, in Hartree
>
> # Use only symmorphic operations
> symmorphi 0
>
> # Definition of the SCF procedure
> nstep   30        # Maximal number of SCF cycles
> 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.
> tolwfr  1.0d-8
>
> # This line added when defaults were changed (v5.3) to keep the previous, old
> behaviour
>   iscf 5
>
> ##########################################
> If anyone has such experience, please instruct me. Thanks in advance.
>