Dear Ronan,

Kwant adds sites to the lead until it reaches the system. This doesn't mean that it duplicates the unit cell.
In fact, the band can be obtained without attaching the lead and the Hamiltonian of the unit cell can be directly obtained by:
lead.cell_hamiltonian(params=params)            #(the lead needs to be finalized here) 
or (syst.leads[0]. cell_hamiltonian(params=params)  )

So you can verify that the unit cell is not duplicated and it is solely defined using the base you defined for the lattice.

I hope this helps,

On Tue, Aug 4, 2020 at 10:49 PM Ronan Viana <> wrote:
Hi, colleagues!

I'm defining the phosphorene unit cell perfectly. However, when the leads are attached to the scattering region, the kwant increases the unit cell, and thus "duplicate" energy levels appear. I'm using the model with 10 interlayer hoppings and 5 interlayer hoppings. Apparently, in the model of 5 interlayer hoppings it doesn't happen! Thank you for your help now.

Abbout Adel