One of sisl goals is an easy interaction between a variety of DFT simulations, much like ASE with a high emphasis on Siesta, while simultaneously providing the tools necessary to perform tight-binding calculations.
However, sisl is far from the only Python package that implements simplistic tight-binding calculations. We are currently aware of 3 established tight-binding methods used in litterature (in random order):
sisl’s philosophy is drastically different in the sense that the Hamiltonian (and other physical quantities described via matrices) is defined in matrix form. As for kwant and pybinding the model is descriptive as shapes define the geometries. Secondly, both kwant and pybinding are self-contained packages where all physics is handled by the scripts them-selves, while sisl can calculate band-structures, but transport properties should be off-loaded to TBtrans.