# Crystalline AlAs : computation of the phonon spectrum

   ndtset   5
#Set 1 : ground state self-consistency

  getwfk1   0            # 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  # Gamma
     qpt4  -0.33333333E+00  0.66666667E+00  0.00000000E+00  # K
     qpt5   0.00000000E+00  0.50000000E+00  0.00000000E+00  # M
#     qpt6  -0.03333333E+00  0.06666667E+00  0.00000000E+00  # Gamma-->K,near Gamma
#     qpt7   0.00000000E+00  0.05000000E+00  0.00000000E+00  # Gamma-->M,near Gamma
#     qpt8  
#     qpt9   
#    qpt10 

#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 4-10 : Finite-wave-vector phonon calculations (defaults for all datasets)

   getwfk   1          # Use GS wave functions from dataset1
   kptopt   3          # Need full k-point set for finite-Q response
   rfphon   1          # Do phonon response
  rfatpol   1 2        # Treat displacements of all atoms
    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

#Definition of the unit cell
    acell    4.6291337970E+00   4.6291362821E+00  12.594409167E+00
    rprim    1.0000000000E+00   0.0000000000E+00  0.0000000000E+00  
            -4.9999978780E-01   8.6602547381E-01  0.0000000000E+00 
             0.0000000000E+00   0.0000000000E+00  1.0000000000E+00

#    rprim    8.6602621211E-01 -4.9999859994E-01  0.0000000000E+00
#             1.7069530102E-06  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   4         # There are 4 atoms
    typat   1 1 1 1   # The first is of type 1 (C), the second is of type 1 (C),etc.
                       
    xred    4.4258838269E-07 -4.4258838269E-07  2.5000000000E-01
            3.3333381468E-01  6.6666618532E-01  2.5000000000E-01
           -4.4258838269E-07  4.4258838269E-07  7.5000000000E-01
            6.6666618532E-01  3.3333381468E-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   12  12  4          
    nshiftk 1
    shiftk  0.0 0.0 0.5

#Definition of the SCF procedure
     iscf   5          # Self-consistent calculation, using algorithm 5
    nstep   50         # Maximal number of SCF cycles
#   diemac   1e6       # 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).