[xcrysden] K-point selection in the xcrysden for graphene

[beda singh]

Hi,
Recently I have started using xcrysden and have some questions regarding
the K-point selection. I have considered a graphene structure with two
carbon atoms in the unit cell. From the K-path selection, I can see the
primitive brillouin zone is hexagonal in structure and I can directly read
coordinates of the symmetric points viz. Gamma, M and K in the reciprocal
lattice. But when I increase the number of carbon atoms in the unit cell
say four atoms or eight stoms, the primitive brillouin zone comes out  not
to be hexagonal but rectangular in shape which is wrong. I have checked my
structure, there is nothing wrong with it and it is indeed graphene. I also
tried by changing the shape and angle of crystall cell but all the time the
primitive brillouin zone comes out rectangular. I am trying to find the
bandstructure of graphene and other graphenelike structures but unable
proceed. Please help me

With Regards
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