#AlAs in hypothetical wurzite (hexagonal) structure
#Structural optimization run

   ndtset   2       # There are 2 datasets in this calculation
# Set 1 : Internal coordinate optimization

 ionmov1   2       # Use BFGS algorithm for structural optimization
  ntime1   100       # Maximum number of optimization steps
 tolmxf1   1.0e-4  # Optimization is converged when maximum force 
                    # (Hartree/Bohr) is less than this maximum
  natfix1   1       # Fix the position of two symmetry-equivalent atoms 
                    #  in doing the structural optimization
  iatfix1   1      # Choose atoms 1 and 2 as the fixed atoms (see discussion)
#strprecon1  0.5

# Set 2 : Lattice parameter relaxation (including re-optimization of
#         internal coordinates)

 dilatmx2   2.83    # Maximum scaling allowed for lattice parameters
 getxred2   -1      # Start with relaxed coordinates from dataset 1
  getwfk2   -1      # Start with wave functions from dataset 1
  ionmov2   2       # Use BFGS algorithm
   ntime2   100      # Maximum number of optimization steps
 optcell2   9      # Fully optimize unit cell geometry, keeping symmetry
  tolmxf2   1.0e-4  # Convergence limit for forces as above
 strfact2   100     # Test convergence of stresses (Hartree/bohr^3) by
                    # multiplying by this factor and applying force
                    # convergence test
  natfix2   1       
  iatfix2   1      
#strprecon2  0.5

#Common input data

#Starting approximation for the unit cell
  acell   2*7.3011855771  10.151105699655 
  angdeg  3*90 


#Definition of the atom types and atoms
nline  10 
ntypat   3 
  znucl   82 22 8 
  natom   5
  typat   1 2 3 3 3

#Starting approximation for atomic positions in REDUCED coordinates
#based on ideal tetrahedral bond angles
   xred  
              0.0000000000E+00  0.0000000000E+00  0.0000000000E+00
              5.0000000000E-01  5.0000000000E-01  5.3139996696E-01
              5.0000000000E-01  5.0000000000E-01  7.6806019671E-02
              5.0000000000E-01  0.0000000000E+00  5.9255820135E-01
              0.0000000000E+00  5.0000000000E-01  5.9255820135E-01
 #Gives the number of bands, explicitely (do not take the default)
  nband   22              # For an insulator (if described correctly as an 
 enunit  2                # insulator by DFT), conduction bands should not
                         # be included in response-function calculations

#Definition of the plane wave basis set
   ecut   40.0            # Maximum kinetic energy cutoff (Hartree)
 ecutsm   0.5            # Smoothing energy needed for lattice paramete
                         # optimization.  This will be retained for
                         # consistency throughout.

#Definition of the k-point grid
 kptopt   1              # Use symmetry and treat only inequivalent points
ngkpt   6 6 6


nshiftk   1              # Use one copy of grid only (default)
 shiftk   0.5 0.5 0.5    # This choice of origin for the k point grid
                         # preserves the hexagonal symmetry of the grid,
                         # which would be broken by the default choice.

#Definition of the self-consistency procedure
# diemix  0.5 
 diemac   6.0            # Model dielectric preconditioner
# ixc     2
  iscf   5              # Use conjugate-gradient SCF cycle
  nstep   40             # Maxiumum number of SCF iterations
 tolvrs   1.0d-10        # Strict tolerance on (squared) residual of the
                         # SCF potential needed for accurate forces and
                         # stresses in the structural optimization, and
                         # accurate wave functions in the RF calculations