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[brsahu@physics.utexas.edu]

Dear Abiniters,

I am testing the ground state calculation of a bulk mono-layer graphene (2-D) 
with vacuum along z-direction (a supercell). In the input file,  I have,

#Definition of the unit cell
acell  2*4.648728 5.0    # This is equivalent to 4.648728 4.648728 5.0
rprim  1.0  0.0        0.0     # Hexagonal supercell(to be scaled by acell)
       0.5 0.8660254000  0.0
       0.0  0.0  1.0

where a=b=4.648728 bohrs and c=5 bohrs (vacuum)

other unit-cell information are

#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 Carbon.


#Definition of the atoms
natom 2           # There are two atoms
typat 2*1          # They both are of type 1, that is, Carbon.
xred              # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom
   0.0 0.0  0.00 # Triplet giving the REDUCED coordinate 1.
   -0.33333333 0.66666667 0.0   # Triplet giving the REDUCED coordinate 2.

ie there are two atoms one at (0,0,0) and  (-1/3,2/3,0)

in the output I do not get the hexagonal symmetry instead I get triclinic

 DATASET    1 : space group P-1 (#  2); Bravais aP (primitive triclinic)
================================================================================
 Values of the parameters that define the memory need for DATASET  1.
   intxc =         0  ionmov =         0    iscf =        17     ixc =        
 2
  lmnmax =         8   lnmax =         4   mband =         5  mffmem =        
 1
P  mgfft =        18   mkmem =       101 mpssoang=         2     mpw =       
270
  mqgrid =      3001   natom =         2    nfft =      5832    nkpt =       
802
  nloalg =         4  nspden =         1 nspinor =         1  nsppol =        
 1
    nsym =         2  n1xccc =         1  ntypat =         1  occopt =        
 1
 PAW method is used; the additional fine FFT grid is defined by:
   mgfftf=        30    nfftf =     27000
================================================================================

am I missing something in the input? What could be wrong?

Sahu