Dear Kwant Developers,

I am a graduate student learning Kwant for my academics project related
purposes.
With reference to the Kwant 1.3.1 Documentation (vide page no.45), the
honeycomb lattice for the zig-zag edged graphene has been defined as:

> graphene = kwant.lattice.general([(1, 0), (sin_30, cos_30)], [(0, 0), (0,
1 / sqrt(3))])

where, as per my understanding,  the first argument to the *general*
function is the list of *primitive vectors* of the lattice; the second one
is the *coordinates of basis atoms*.

According to the physics of graphene, the carbon-carbon bond length is
approximately 0.142 nm. But after running the above code, I checked that
the C-C bond length of the honeycomb lattice is coming as 1/sqrt(3) nm i.e.
~0.58 nm. Therefore, I am feeling quite confused as I am failing to
understand where I am going wrong or whether am overlooking any fundamental
concepts.
I had also raised my query earlier here, regarding defining the lattice for
armchair edged graphene (vide Volume 59, Issue 6), but it seems that
unfortunately it has missed your notice. So my understandings on this
specific domain are still quite hazy.

It would be of great help if you look into the matter and  kindly guide me
to find solution for the above mentioned queries.

Thanks
Regards
Arunabha Ghoshal

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