# Crystalline AlAs : computation of the phonon spectrum

   ndtset   4
#Set 1 : ground state self-consistency

#   prtwf1    1            # Output wavefunction
  getwfk1   0
#  irdwfk1   1            # Cancel default
  kptopt1   1            # Automatic generation of k points, taking
                         # into account the symmetry
    nqpt1   0            # Cancel default
  tolvrs1   1.0d-18      # SCF stopping criterion (modify default)
  rfphon1   0            # Cancel default
 
#Q vectors for all datasets

#Complete set of symmetry-inequivalent qpt chosen to be commensurate
# with kpt mesh so that only one set of GS wave functions is needed.
#Generated automatically by running GS calculation with kptopt=1,
# nshift=0, shiftk=0 0 0 (to include gamma) and taking output kpt set
# file as qpt set. Set nstep=1 so only one iteration runs.

     nqpt   1            # One qpt for each dataset (only 0 or 1 allowed)
                         # This is the default for all datasets and must
                         #  be explicitly turned off for dataset 1.


      qpt2   0.00000000E+00  0.00000000E+00  0.00000000E+00
      qpt3   0.00000000E+00  0.00000000E+00  0.00000000E+00

      qpt4   1.00000000E-01  1.00000000E-01  2.50000000E-01
#      qpt5   3.00000000E-01  1.00000000E-01  2.50000000E-01
#      qpt6   5.00000000E-01  1.00000000E-01  2.50000000E-01
#      qpt7  -3.00000000E-01  1.00000000E-01  2.50000000E-01
#      qpt8  -1.00000000E-01  1.00000000E-01  2.50000000E-01
#      qpt9   1.00000000E-01  3.00000000E-01  2.50000000E-01
#      qpt10   3.00000000E-01  3.00000000E-01  2.50000000E-01
#      qpt11   5.00000000E-01  3.00000000E-01  2.50000000E-01
#      qpt12  -3.00000000E-01  3.00000000E-01  2.50000000E-01
#      qpt13  -1.00000000E-01  3.00000000E-01  2.50000000E-01
#      qpt14   1.00000000E-01  5.00000000E-01  2.50000000E-01
#      qpt15   3.00000000E-01  5.00000000E-01  2.50000000E-01
#      qpt16   5.00000000E-01  5.00000000E-01  2.50000000E-01
      
#Set 2 : Response function calculation of d/dk wave function 

    iscf2   -3         # Need this non-self-consistent option for d/dk
  kptopt2   2          # Modify default to use time-reversal symmetry
  rfphon2   0          # Cancel default
  rfelfd2   2          # Calculate d/dk wave function only
  tolvrs2   0.0        # Cancel default for d/dk
  tolwfr2   1.0d-22    # Use wave function residual criterion instead

#Set 3 : Response function calculation of Q=0 phonons and electric field pert.

  getddk3   2          # d/dk wave functions from last dataset
  kptopt3   2          # Modify default to use time-reversal symmetry
  rfelfd3   3          # Electric-field perturbation response only

#Sets 4-16 : Finite-wave-vector phonon calculations (defaults for all datasets)

   getwfk   1          # Use GS wave functions from dataset1
#   prtwf    0          # Do not output wavefunctions
   kptopt   3          # Need full k-point set for finite-Q response
   rfphon   1          # Do phonon response
  rfatpol   3 4        # Treat displacements of all atoms 1-->natom
    rfdir   1 1 1      # Do all directions (symmetry will be used)
   tolvrs   1.0d-8     # This default is active for sets 3-10

#######################################################################
#Common input variables

   prtvol   1

#Definition of the unit cell
    acell    4.6290815084E+00  4.6290815321E+00  1.2602990871E+01
    rprim    9.9999999944E-01  3.3568380980E-05  0.0000000000E+00
             -4.9997119449E-01  8.6604203402E-01  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   4         # There are 4 atoms
    typat   1 1 1 1   # The first is of type 1 (Al), the second is of type 2 (As).
                     
     xred   -1.7328114236E-04  1.7328162585E-04  2.5000000000E-01
             3.3315458644E-01  6.6684541163E-01  2.5000000000E-01
             1.7328114236E-04 -1.7328162585E-04  7.5000000000E-01
             6.6684541356E-01  3.3315458837E-01  7.5000000000E-01

#Gives the number of band, explicitely (do not take the default)
    nband  12        

#Exchange-correlation functional

      ixc   1             # LDA Teter Pade parametrization
   occopt   4
   tsmear   0.05

#Definition of the planewave basis set

     ecut   36.0           # Maximal kinetic energy cut-off, in Hartree

#Definition of the k-point grid
    ngkpt   10  10  4          
  nshiftk   1              # Use one copy of grid only (default)
   shiftk   0.5 0.5 0.5    # This gives the usual fcc Monkhorst-Pack grid

#Definition of the SCF procedure
     iscf   7          # Self-consistent calculation, using algorithm 5
    nstep   600        # Maximal number of SCF cycles
#   diemac   9.0        # 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.
                       # The dielectric constant of AlAs is smaller that the one of Si (=12).