The single-site Green's function and Krein's theorem.

An important step in electronic structure calculations using multiple-scattering theory is obtaining the density of states for the central site from the Green's function for that site. We have found that the Krein's spectral displacement function for the central site contributes significantly to the understanding of these calculations. We argue that these insights can lead to improvements in the robustness of MST electronic structure codes without negatively impacting their performance.