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["Yiming Zhang" <zhangy4@rpi.edu>]

Dear ABINIT users,

 

I am trying to calucalte the direct band gap at gamma for diamond, as a test of the GW method. While LDA give the gap of 5.5 eV as expected, GW perturbation gives the gap of 11.4 eV. While both experiment and previous GW study shows the gap around 7.5 eV.

 

I have attached the job input file, is there anything wrong? It will take couple minutes to finish in a modern CPU. Appreciate your time.

 

Regards,

Yiming Zhang

 

ndtset      3

# Definition of parameters for the calculation of the KSS file
nbandkss1   -1         # Number of bands in KSS file (-1 means the maximum 
possible)
nband1      12         # Number of (occ and empty) bands to be computed
istwfk1     11*1

# Calculation of the screening (epsilon^-1 matrix)
optdriver2  3        # Screening calculation
getkss2     -1       # Obtain KSS file from previous dataset
nband2      30       # Bands to be used in the screening calculation
ecutwfn2    2.1      # Cut-off energy of the planewave set to represent the 
wavefunctions
ecuteps2    3.6      # Cut-off energy of the planewave set to represent the 
dielectric matrix
ppmfrq2    16.7 eV  # Imaginary frequency where to calculate the screening

# Calculation of the Self-Energy matrix elements (GW corrections)
optdriver3  4        # Self-Energy calculation
getkss3     -2       # Obtain KSS file from dataset 1
getscr3     -1       # Obtain SCR file from previous dataset
nband3      50       # Bands to be used in the Self-Energy calculation
ecutwfn3     5.0     # Planewaves to be used to represent the wavefunctions
ecutsigx3     6.0     # Dimension of the G sum in Sigma_x
                     # (the dimension in Sigma_c is controlled by npweps)
nkptgw3      1                # number of k-point where to calculate the GW 
correction
kptgw3                       # k-points
 0.000   0.000    0.000
bdgw3       4  5             # calculate GW corrections for bands from 4 to 5


# Data common to the three different datasets

# Definition of the unit cell: fcc
acell  3*6.710        # lattice constant Si 5.43095 Diamond 3.56683 
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 6          # 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 k-point grid
kptopt  0            # Option for the automatic generation of k points,
nkpt    11
       kpt 
              0.00000000E+00  0.00000000E+00  0.00000000E+00
             -1.25000000E-01 -2.50000000E-01  0.00000000E+00
             -1.25000000E-01  5.00000000E-01  0.00000000E+00
             -2.50000000E-01 -3.75000000E-01  0.00000000E+00
             -1.25000000E-01 -3.75000000E-01  1.25000000E-01
             -1.25000000E-01  2.50000000E-01  0.00000000E+00
             -2.50000000E-01  3.75000000E-01  0.00000000E+00
             -3.75000000E-01  5.00000000E-01  0.00000000E+00
             -2.50000000E-01  5.00000000E-01  1.25000000E-01
             -1.25000000E-01  0.00000000E+00  0.00000000E+00
             -3.75000000E-01  0.00000000E+00  0.00000000E+00

# Use only symmorphic operations
symmorphi 0

# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 32.0          # Maximal kinetic energy cut-off, in Hartree

# Definition of the SCF procedure
nstep   40        # Maximal number of SCF cycles
toldfe  1.0d-6    # Will stop when this tolerance is achieved on total energy
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.


# This line added when defaults were changed (v5.3) to keep the previous, old 
behaviour
  iscf 5