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[denis.rideau@st.com]

I do not succeed to compute the total Band structure with ABINIT. One can not 
obtain the GW correction at a given kpoint.

I was said that it is possible to get electronic energies on a mesh of k 
points and to plot the quasi-particle correction
to the LDA value as a function of the LDA energy, in the spirit of
Fig. 1 of Phys. Rev. B34, 5390 (1986),
then make a linear interpolation for each group of points
corresponding to one band, and use that interpolation to correct
the LDA band structure at every point.

When I try to do so I obtain: 

 calculating <nk|sigma|nk>
 k =    0.000   0.000   0.000
 bands n = from   1 to   8

 **error gw 103: q = k - k1 + g0 not found.
 ikbz  =  193 0.0E+0 0.0E+0 0.0E+0
 ik1bz =  257 0.0E+0 0.2 0.0E+0
 kmk1  =  0.0E+0 -0.2 0.0E+0
STOP: q = k - k1 + g0 not found



===>My question is: What is the most efficient way to obtain a mesh of k 
points and how to do it?

I am very appreciated for any help!

Denis Rideau


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%5
PS: The .in used was for instance:

# Crystalline silicon
# Calculation of the GW correction to the direct band gap in Gamma
# Dataset 1: ground state calculation 
# Dataset 2: calulcation of the kss file for only Gamma point
# Dataset 3: calculation of the screening (epsilon^-1 matrix for W)
# Dataset 4: calculation of the Self-Energy matrix elements (GW corrections)

# Definition of the unit cell: fcc
acell  3*10.217        # This is equivalent to   10.217 10.217 10.217
rprim  0.0  0.5  0.5   # FCC primitive vectors (to be scaled by acell)
       0.5  0.0  0.5   
       0.5  0.5  0.0

# Definition of the atom types
ntypat  1         # There is only one type of atom
znucl 14          # 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 Silicon.
                         
# Definition of the atoms
natom 2           # There are two atoms
typat  1 1        # They both are of type 1, that is, Silicon.
xred              # Reduced coordinate of atoms
      0.0  0.0  0.0
      0.25 0.25 0.25

# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 8.0          # Maximal kinetic energy cut-off, in Hartree

# Definition of the SCF procedure
nstep   10        # 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.

ndtset      4

# Dataset1: usual self-consistent ground-state calculation
kptopt1  0 # K-points will be provided
nkpt1    19 # 
kpt1
      -0.375     0.125     -0.250
      -0.500     0.125     -0.375
      -0.125     0.375      0.000
      -0.250     0.375     -0.125
      -0.125     0.125      0.000
      -0.250     0.125     -0.125
      -0.125     0.250     -0.125
      -0.375     0.250     -0.125
      -0.375     0.250     -0.375
      -0.125     0.000     -0.125
      -0.375     0.000     -0.375
       0.000     0.000      0.000
      -0.250     0.000     -0.250
      -0.500     0.000     -0.500
       0.000     0.250      0.000
      -0.250     0.250      0.000
      -0.250     0.250     -0.250
      -0.500     0.250     -0.250
       0.000     0.500      0.000

istwfk1  1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1  # 
# Definition of the SCF procedure
toldfe1  1.0d-6    # Will stop when this tolerance is achieved on total energy
prtden1  1         # Print out density

# Dataset2: calculation of kss file
# Definition of k-points
kptopt2  0 # K-points will be provided
nkpt2    19 # A set of 19 k-points containing Gamma
kpt2
      -0.375     0.125     -0.250
      -0.500     0.125     -0.375
      -0.125     0.375      0.000
      -0.250     0.375     -0.125
      -0.125     0.125      0.000
      -0.250     0.125     -0.125
      -0.125     0.250     -0.125
      -0.375     0.250     -0.125
      -0.375     0.250     -0.375
      -0.125     0.000     -0.125
      -0.375     0.000     -0.375
       0.000     0.000      0.000
      -0.250     0.000     -0.250
      -0.500     0.000     -0.500
       0.000     0.250      0.000
      -0.250     0.250      0.000
      -0.250     0.250     -0.250
      -0.500     0.250     -0.250
       0.000     0.500      0.000

istwfk2  1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1  # 
# Definition of the SCF procedure
iscf2    -2             # Non self-consistent calculation
getden2  -1             # Read previous density file
tolwfr2  1.0d-1         # It's not important, as later there is a diago
nband2   9
# Definition of parameters for the calculation of the kss file
nbndsto2 100        # Number of bands to store in KSS file
ncomsto2 169        # Number of plane waves 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      25       # Bands to be used in the screening calculation
npwwfn3     137       # Planewaves to be used to represent the wavefunctions
npweps3     169      # Dimension of the screening matrix
plasfrq3    16.7 eV  # Imaginary frequency where to calculate the screening

# Dataset4: Calculation of the Self-Energy matrix elements (GW corrections)
optdriver4  4        # Self-Energy calculation
getkss4     -2       # Obtain KSS file from dataset 1
geteps4     -1       # Obtain EM1 file from previous dataset
nband4      100      # Bands to be used in the Self-Energy calculation
npwwfn4     137      # Planewaves to be used to represent the wavefunctions
npwmat4     169      # Dimension of the G sum in Sigma_x
                     # (the dimension in Sigma_c is controlled by npweps)
ngwpt4      19                # number of k-point where to calculate the GW 
correction
kptgw4                       # k-points
      -0.375     0.125     -0.250
      -0.500     0.125     -0.375
      -0.125     0.375      0.000
      -0.250     0.375     -0.125
      -0.125     0.125      0.000
      -0.250     0.125     -0.125
      -0.125     0.250     -0.125
      -0.375     0.250     -0.125
      -0.375     0.250     -0.375
      -0.125     0.000     -0.125
      -0.375     0.000     -0.375
       0.000     0.000      0.000
      -0.250     0.000     -0.250
      -0.500     0.000     -0.500
       0.000     0.250      0.000
      -0.250     0.250      0.000
      -0.250     0.250     -0.250
      -0.500     0.250     -0.250
       0.000     0.500      0.000
bdgw4       1  8             # calculate GW corrections 
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
       1  8      
zcut4       0.1 eV           # parameter to avoid poles