[CPMD-list] Explanation for SYSTEM section

[MENON, MAHESH]

Hello Colleagues,

I did not understand clearly the &SYSTEM -&END section for the following
input.

&SYSTEM 
   POINT GROUP 
    AUTO 
   SYMMETRY 
    4 
   CELL 
    2.802    1.0    5.7155     1.0  1.0  1.0    (alat=3.962,
c/a=7*sqrt(2/3)) 
   CUTOFF 
    40.000 
   ANGSTROMS 
   STATES 
    22 
   SCALE 
   TESR 
     3 
   KPOINTS MONKHORST-PACK FULL 
    7 7 1 
 &END

The  above input was from one of the examples given in Prof. Hutter's
homepage. The input says, the system is hexagonal (since SYMMETRY = 4). For
hexagonal, a = b ≠ c and Alpha = Beta= 90 and Gama = 120. But in this
example, it is taken as COS (Alpha) = 1.0, which means Alpha = 0. 

Could anyone explain to me this?.. Also I would appreciate if some of you
can explain to me how the unit cell is repeated in this case.

Thanks in advance,
Sincerely,

Mahesh