Hi Joe

If I understand your question correctly then you need to do do a k-space integration; something like:

     ∑_n ∫ E_n(k) f(E_n(k)) dk

Where the sum runs over all the bands, the integral runs over the Brillouin zone and 'f' is the occupation at energy E (e.g. Fermi-Dirac). In this way you count the energy contribution for each state, weighted by its occupation. Note that we have elided the density of states, as we are integrating directly in momentum space, as opposed to in energy, and the density of states in 1D is constant in k.

Does that make sense?

It does make sense and helps a lot.

Is there a way to calculate E_n(k) of a 2D infinite system in kwant? 2D translational symmetric systems can't be finalized and cell_hamiltionian and inter_cell_hopping don't work with wraparound either.

Best regards,

Jannis

${\displaystyle \displaystyle \int }$