- Lanczos Diagonalization:

The keyword LANCZOS DIAGONALIZATION is required for computing the ground state wavefunction of metals in combination with the FREE ENERGY FUNCTIONAL keyword, but it also works on insulators. With this setup actually there is no full diagonalization performed like in the KOHN-SHAM ENERGIES run from above, but the density is updated after only one Lanczos step. Over time the states will converge as the density updates become smaller, the procedure speeds up and the orbitals will become diagonal as well.