# Crystalline silicon
# Preparation of the kss and scr files for the convergence study of the GW correction
# Dataset 1: ground state calculation 
# Dataset 2: calculation of the kss file 
# Dataset 3: calculation of the screening (epsilon^-1 matrix for W)
# Dataset 4: calculation of the GW correction at Gamma


ndtset  4

#Definition of the k-point grid density
kptopt   1            # Option for the automatic generation of k points
ngkpt    8 8 8        # converged value for GS calculation

# Dataset1: usual self-consistent ground-state calculation
# Definition of the k-points
nkpt1     60
nshiftk1  4
shiftk1  0.5 0.5 0.5  # This grid is the most economical
         0.5 0.0 0.0
         0.0 0.5 0.0
         0.0 0.0 0.5
iscf1 5
toldfe1 1.0d-8
prtden1  1         # Print out density

# Dataset2: calculation of kss file
## Definition of k-points

nkpt2    85             # A set of 85 k-points containing Gamma
nshiftk2  4
shiftk2  0.0 0.0 0.0    # This grid contains the Gamma point
         0.0 0.5 0.5
         0.5 0.0 0.5
         0.5 0.5 0.0
istwfk2  85*1             # Option needed for Gamma
iscf2    -2             # Non self-consistent calculation
tolwfr2  1.0d-10        # Still get it converged
getden2  -1             # Read previous density file
nband2   155            # number of bands to treat at each k-point

##Definition of parameters for the generation of the kss file
kssform  3           # Kohn Sham Structure will be generated through the conjugate gradient algorithm
nbandkss2 150        # Number of bands to store in KSS file
nbdbuf  5            # Number of the bands of highest in energy which will be used as buffer

# Dataset3: Calculation of the screening (epsilon^-1 matrix)
optdriver3  3        # Screening calculation
getkss3     -1       # Obtain KSS file from previous dataset
nband3      50       # Bands to be used in the screening calculation
ecutwfn3    6.0      # Planewaves to be used to represent the wavefunctions
ecuteps3    6.0      # Dimension of the screening matrix
ppmfrq3    16.7 eV   # Imaginary frequency where to calculate the screening

nshiftk3  4             # k-grid similar to that used in kss calculation
shiftk3  0.0 0.0 0.0    # This grid contains the Gamma point
         0.0 0.5 0.5
         0.5 0.0 0.5
         0.5 0.5 0.0
istwfk3  85*1             # Option needed for Gamma

# Dataset4: Calculation of the Self-Energy matrix elements (GW corrections)
optdriver4   4        # Self-Energy calculation
getkss4     -2        # Obtain KSS file from dataset 1
getscr4     -1        # Obtain SCR file from previous dataset
nband4       100      # Bands to be used in the Self-Energy calculation
ecutwfn4     6.0      # Planewaves to be used to represent the wavefunctions
ecutsigx4    6.0      # 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
  0.000    0.000    0.000    # (Gamma)
bdgw4       1  5             # calculate GW corrections for bands from 1 to 5

nshiftk4  4             # k-grid similar to that used in kss calculation
shiftk4  0.0 0.0 0.0    # This grid contains the Gamma point
         0.0 0.5 0.5
         0.5 0.0 0.5
         0.5 0.5 0.0
istwfk4  85*1             # Option needed for Gamma

# Definition of the unit cell: fcc
acell  3*10.17         # converged values form structure optimization
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
      1/4  1/4  1/4

# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 20.0          # Maximal kinetic energy cut-off, in Hartree, for well converged gs calculation 

#Choice for exchange corelation term
ixc  1

#Spin orbit coupling option
nspinor 1     #Force to exclude the SO part

# Use only symmorphic operations
symmorphi 0

#Set inclvkb = 0 for psp with more than one projector per l-state
inclvkb  0

# Definition of the SCF procedure
nstep   100        # 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.
prtvol 1           # all k-point will be printed out