This can construct the tight-binding model and calculate energies

The Reduced-Shifted Conjugate-Gradient Method method to calculate the element of the Green's function matrix. See, Y. Nagai, Y. Shinohara, Y. Futamura, and T. Sakurai,[arXiv:1607.03992v2 or DOI:10.7566/JPSJ.86.014708]. http://dx.doi.org/10.7566/JPSJ.86.014708