#Prepare the computation of linear and non-linear optic properties
#of GaAs crystal : ground-state with few bands,
#then non-SCF with a larger number of bands, then ddk for different directions
#Note that the k point sampling shoud be finer for significant results. The cut-off energy is also too low.

# ndtset 6

#First dataset : SC run with kpoints in the IBZ
#   iscf1  3
  nband1  48     
  nstep1 3000   
 kptopt1 1
 nbdbuf1 0
 prtden1 1   getden1 0   getwfk1 0    #! Usual file handling data

#Second dataset : NSC run with large number of bands, and points in the IBZ
    iscf2 -2  
   nband2 60  #! This number of bands might be too low for non-linear optics and real part of linear optics
   nstep2 3000
  kptopt2  1
  getwfk2  1   getden2 1   #! Usual file handling data

#Third dataset : NSC run with large number of bands, and points in the the full BZ
    iscf3 -2  
   nband3 60  #! This number of bands might be too low for non-linear optics and real part of linear optics 
   nstep3 3000
  kptopt3  3
  getwfk3  2   getden3 1   #! Usual file handling data


#Fourth dataset : ddk response function along axis 1
   iscf4 -3
  nband4 60   #! This number of bands might be too low for non-linear optics and real part of linear optics
  nstep4  1  nline4  0
 kptopt4  3

   nqpt4  1  qpt4  0.0d0 0.0d0 0.0d0 
  rfdir4  1 0 0
 rfelfd4  2
 getwfk4  3

#Fifth dataset : ddk response function along axis 2
   iscf5 -3
  nband5 60   #! This number of bands might be too low for non-linear optics and real part of linear optics
  nstep5  1  nline5  0
 kptopt5  3

   nqpt5  1  qpt5  0.0d0 0.0d0 0.0d0
  rfdir5  0 1 0
 rfelfd5  2
 getwfk5  3

# Sixth dataset : ddk response function along axis 3
   iscf6 -3
  nband6 60   #! This number of bands might be too low for non-linear optics and real part of linear optics
  nstep6  1  nline6  0
 kptopt6  3

   nqpt6  1  qpt6  0.0d0 0.0d0 0.0d0
  rfdir6  0 0 1
 rfelfd6  2
 getwfk6  3

     acell    3.5235615817E+01  3.5235615817E+01  8.0016991685E+00
     rprim    1.0000000000E+00  0.0000000000E+00  0.0000000000E+00
              0.0000000000E+00  1.0000000000E+00  0.0000000000E+00
              0.0000000000E+00  0.0000000000E+00  1.0000000000E+00
#Definition of the atom types
   ntypat   1         # There are two types 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, type 1 is the Aluminum,
                      # type 2 is the Arsenic.

#Definition of the atoms
    natom   20         # There are two atoms
    typat   20*1       # The first is of type 1 (Al), the second is of type 2 (As).

    xangst    2.0316014574E+00  2.4216927481E-23  4.2710202574E-02
              1.6328889522E+00  1.1869210885E+00  3.5585739095E+00
              1.6328889522E+00  1.1869210885E+00  2.1568539915E+00
              6.2717218880E-01  1.9262002753E+00  1.4395886175E+00
              6.2717218880E-01  1.9262002753E+00  4.1522435857E-02
             -6.2717218880E-01  1.9262002753E+00  3.5567470413E+00
             -6.2717218880E-01  1.9262002753E+00  2.1586808597E+00
             -1.6328889522E+00  1.1869210885E+00  1.4414154856E+00
             -1.6328889522E+00  1.1869210885E+00  3.9695567697E-02
             -2.0316014574E+00  2.4216927481E-23  3.5555592746E+00
             -2.0316014574E+00  2.4216927481E-23  2.1598686264E+00
             -1.6328889522E+00 -1.1869210885E+00  1.4414154856E+00
             -1.6328889522E+00 -1.1869210885E+00  3.9695567697E-02
             -6.2717218880E-01 -1.9262002753E+00  3.5567470413E+00
             -6.2717218880E-01 -1.9262002753E+00  2.1586808597E+00
              6.2717218880E-01 -1.9262002753E+00  1.4395886175E+00
              6.2717218880E-01 -1.9262002753E+00  4.1522435857E-02
              1.6328889522E+00 -1.1869210885E+00  3.5585739095E+00
              1.6328889522E+00 -1.1869210885E+00  2.1568539915E+00
              2.0316014574E+00  2.4216927481E-23  1.4384008508E+00

#Exchange-correlation functional

      ixc   1             # GGA PBE

#Definition of the planewave basis set

   occopt   3
   tsmear   0.001
     ecut   22.0           # Maximal kinetic energy cut-off, in Hartree
pawecutdg   50

   ecutsm   0.5
  dilatmx   1.03

#Definition of the k-point grid
    ngkpt   1  1  32
  nshiftk   1              # Use one copy of grid only (default)
   shiftk   0.0 0.0 0.5    # 0.0  0.0  0.5 # Note!!!! the k-mesh should have same k-points as el-phonon calculation.
           # 0.0 0.5 0.0
           # 0.5 0.0 0.0
           # 0.5 0.5 0.5

#Definition of the SCF procedure
     iscf   17           # Self-consistent calculation, using algorithm 5
#    nstep   3000        # Maximal number of SCF cycles
#   diemac   12.0       # Although this is not mandatory, it is worth to
   diemix   0.4        # precondition the SCF cycle. The model dielectric
                       # function used as the standard preconditioner
                       # is described in the "dielng" input variable section.
                       # The dielectric constant of AlAs is smaller that the one of Si (=12).
   iprcel   45
    nline    6
   nnsclo    2

   wfoptalg  1
   nbdblock  4
   timopt    2

# SCF condition

   tolvrs1 1.0e-15
   tolwfr1 0

   tolwfr  1.e-20
   tnons   12*0.0