It has nothing to do with Hydrogens in the system. As a matter of fact,
hydrogens would open the gap - it would be graphane, not graphene. The input
seems fine to me, and it it most likely because your specification of band
lines is incorrect. If you choose

BandLinesScale   ReciprocalLatticeVectors

then G=(0,0,0), K=(0,-0.5,0) and M=(0.5,0,0) (Check the figure on page 25 of
Saito and Dresselhaus's book).

Best regards,

Marcos

On Tue, Jun 14, 2011 at 9:11 AM, deepak srinivasan <[email protected]>wrote:

> Hi
>
> i think this is a sample program coming along with siesta
>
> as for as the band gap being large it is due to the carbons not being
> terminated by hydrogens or any other such atom
>
> Terminate the two atoms with hydrogen and observe the difference
> --
> regards
> deepak
> 3rd Year Under Graduate
> Electronics Design and Manufacturing
> IIIT (D&M),Kancheepuram
> IIT Madras Campus,Chennai
>

Responder a