# (7,0) Carbon Nanotube : computation of the total energy
# bond legth a = 1.421 angstrom

#Definition of the unit cell
acell 32.90441114 32.90441114 4.2630000000 angstrom    # The size of unit cell in angstrom


#Definition of the atom types
ntypat 1          # There is only one type 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, the only type is Silicon.
                         

#Definition of the atoms
natom 28          # There are 28 atoms
typat 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
                  # They all are of type 1, that is, Carbon.

xangst            # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom
                  # Triplet giving the cartesian coordinates of all atoms, in Angstrom
19.1942398700  16.4522055700  0.0000000000
18.9226930700  17.6419296700  0.7105000000
18.1618359700  18.5960142700  0.0000000000
17.0623655700  19.1254912700  0.7105000000
15.8420455700  19.1254912700  0.0000000000
14.7425751700  18.5960142700  0.7105000000
13.9817180700  17.6419296700  0.0000000000
13.7101712700  16.4522055700  0.7105000000
13.9817180700  15.2624814700  0.0000000000
14.7425751700  14.3083968700  0.7105000000
15.8420455700  13.7789198700  0.0000000000
17.0623655700  13.7789198700  0.7105000000
18.1618359700  14.3083968700  0.0000000000
18.9226930700  15.2624814700  0.7105000000
18.9226930700  17.6419296700  2.1315000000
18.1618359700  18.5960142700  2.8420000000
17.0623655700  19.1254912700  2.1315000000
15.8420455700  19.1254912700  2.8420000000
14.7425751700  18.5960142700  2.1315000000
13.9817180700  17.6419296700  2.8420000000
13.7101712700  16.4522055700  2.1315000000
13.9817180700  15.2624814700  2.8420000000
14.7425751700  14.3083968700  2.1315000000
15.8420455700  13.7789198700  2.8420000000
17.0623655700  13.7789198700  2.1315000000
18.1618359700  14.3083968700  2.8420000000
18.9226930700  15.2624814700  2.1315000000
19.1942398700  16.4522055700  2.8420000000


#Definition of the planewave basis set
ecut  20.0         # Maximal kinetic energy cut-off, in Hartree

#Exchange-correlation functional
ixc 7             # LDA Teter Pade parametrization

#Definition of the k-point grid
kptopt 1          # Option for the automatic generation of k points, taking
                  # into account the symmetry
ngkpt 1 1 4       # This is a 1x1x4 grid based on the primitive vectors


#Definition of the SCF procedure
nstep 100         # Maximal number of SCF cycles
toldfe 1.0d-4     # 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 carbon.
diemix 0.5        # function used as the standard preconditioner
                  # is described in the "dielng" input variable section.
                  # Here, we follow the prescriptions for molecules 
                  # in a big box