ndtset 1

#Optimization of acell, rprim
optcell 2
#BFGS scheme
ionmov  2

ntime  10
dilatmx 1.20
ecutsm  0.5

prtgeo 1

#Definition of the k-point grids
kptopt 1          # Option for the automatic generation of k points, taking
                  # into account the symmetry
nshiftk 4
shiftk  0.5 0.5 0.5  # These shifts will be the same for all grids
        0.5 0.0 0.0
        0.0 0.5 0.0
        0.0 0.0 0.5

ngkpt1  4 4 4 

getwfk -1         # This is to speed up the calculation, by restarting
                  # from previous wavefunctions, transferred from the old 
                  # to the new k-points.

ecut 15.0          # Maximal kinetic energy cut-off, in Hartree

#Definition of the SCF procedure
nstep 10          # Maximal number of SCF cycles
toldfe 1.0d-6     # Will stop when, twice in a row, the difference 
                  # between two consecutive evaluations of total energy 
                  # differ by less than toldfe (in Hartree) 
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.
                  # Here, we follow the prescription for bulk silicon.

ntypat 1          # There is only one type of atom
znucl  6          # Carbon
#Definition of the unit cell
acell 3*1.0 angstrom
rprim    7.5117310187   -4.3368999257    0.0000000000
         0.0000000000    8.6915984379    0.0000000000
         0.0000000000    0.0000000000    4.2134161359
                       
#Definition of the atoms
natom 20          # There are two atoms
typat 20*1        # They both are of type 1, that is, Silicon.
xangst              # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom
  1.58119     1.14880     2.12700
  0.60396     1.85880     1.41800
  0.60396     1.85880     0.00000
 -0.60396     1.85880    -0.70900
 -0.60396     1.85880     2.12700
 -1.58119     1.14880     1.41800
 -1.58119     1.14880     0.00000
 -1.95446     0.00000    -0.70900
 -1.95446     0.00000     2.12700
 -1.58119    -1.14880     1.41800
 -1.58119    -1.14880     0.00000
 -0.60396    -1.85880    -0.70900
 -0.60396    -1.85880     2.12700
  0.60396    -1.85880     1.41800
  0.60396    -1.85880     0.00000
  1.58119    -1.14880    -0.70900
  1.58119    -1.14880     2.12700
  1.95446    -0.00000     1.41800
  1.95446    -0.00000     0.00000
  1.58119     1.14880    -0.70900