The following two variables for the energy cutoffs are mandatory, and have no default values.
All energies are in Rydbergs.
Set the energy cutoffs to be 70 and 10 Rydbergs. The generation of the starting guess is not optimized, and can become very time consuming if the submatrix is too large. The accuracy of the eigenvalues is normally at least as good, often an order of magnitude better. There is no point in converging the eigenvectors for a Hamiltonian which is not nearly close to self-consistency. In this case, only the minimum number of bands are computed, and the diagonalization scheme uses this bandgap for performance optimization.