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[sara yazdani <sarayazdani@yahoo.com>]

Dear Sir,

I have got some problems regarding the supercell of a hexagonal lattice:

- In the enclosed article, for the mono-layer, they have shown a single layer 
cut from the wurtzite crystal.
http://arxiv.org/PS_cache/cond-mat/pdf/0511/0511274v3.pdf

a) According to what they've done, how many atoms we should consider in the 
supercell for a single layer? Is it enough to take only two atoms in the 
unit, which we increase the dimention along c only? (like t43.in in the 
tutorial)

b) When I consider a supercell in wurtzite structure, if I put angdeg: 90 90 
120 and specify xred accordingly, the run will finish, but delivers more 
than1000 warning of "nsymat"(even if I put nsym=0). But when I put the angdeg 
90 90 90 and change the xred accoingly the results come out with no symmetry 
warning and it has also good results. Why does it happen while it is said 
that "the super cell should be chosen according to the primitive cell"? 
(natom=12 or 26)

c) I have calculated the energy of the single atoms and the total energy of 
the bulk system same as the article, but the binding energy is off, what 
should I do?

Regards,
Sara