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# Crystalline SiO2 : computation of the phonon spectrum

   ndtset   18
#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
     qpt4      1.66666667E-01  0.00000000E+00  0.00000000E+00
     qpt5      3.33333333E-01  0.00000000E+00  0.00000000E+00
     qpt6      5.00000000E-01  0.00000000E+00  0.00000000E+00
     qpt7      1.66666667E-01  1.66666667E-01  0.00000000E+00
     qpt8      3.33333333E-01  1.66666667E-01  0.00000000E+00
     qpt9      5.00000000E-01  1.66666667E-01  0.00000000E+00
     qpt10     -3.33333333E-01  1.66666667E-01  0.00000000E+00
     qpt11     -1.66666667E-01  1.66666667E-01  0.00000000E+00
     qpt12     3.33333333E-01  3.33333333E-01  0.00000000E+00
     qpt13     5.00000000E-01  3.33333333E-01  0.00000000E+00
     qpt14     -3.33333333E-01  3.33333333E-01  0.00000000E+00
     qpt15     5.00000000E-01  5.00000000E-01  0.00000000E+00
     qpt16     5.00000000E-01  3.33333333E-01  1.66666667E-01
     qpt17     -3.33333333E-01  3.33333333E-01  1.66666667E-01
     qpt18     -3.33333333E-01  5.00000000E-01  1.66666667E-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
  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 4-18 : 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 3        # 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   3*8.6542          # This is equivalent to   10.61 10.61 10.61
    rprim   0.0  0.5  0.5   # In lessons 1 and 2, these primitive vectors 
            0.5  0.0  0.5   # (to be scaled by acell) were 1 0 0  0 1 0  0 0 1 
            0.5  0.5  0.0   # that is, the default.

#Definition of the atom types
   ntypat   2         # There are two types of atom
    znucl   14 8     # 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   3         # There are two atoms
    typat   1 2 2      # The first is of type 1 (Si), the second is of type 2 (O).

     xred   0.0  0.0  0.0
            0.25 0.25 0.25
            0.75 0.75 0.75

#Gives the number of band, explicitely (do not take the default)
    nband   16

#Exchange-correlation functional

      ixc   11             # GGA, Perdew-Burke-Ernzerhof GGA functional

#Definition of the planewave basis set

     ecut   40           # Maximal kinetic energy cut-off, in Hartree

#Definition of the k-point grid
    ngkpt   6  6  6
  nshiftk   1              # Use one copy of grid only (default)
   shiftk   0.0 0.0 0.0    # This gives the usual fcc Monkhorst-Pack grid
#Definition of the SCF procedure
     iscf   7          # Self-consistent calculation, using algorithm 5
    nstep   125         # 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.
                       # The dielectric constant of AlAs is smaller that the one of Si (=12).
# add to conserve old < 6.7.2 behavior for calculating forces at each SCF step
 optforces 1