Absolute and Approximate Calculations of Electron-Energy-Loss Spectroscopy Edge Thresholds

Systematic studies of binding energies for the electron excitation of core levels for atoms, molecules and solids have been calculated with various density functional theories. The Generalized gradient approximation provided the most accurate description of the absolute binding energies when spin polarization was included. Relative core level shifts could be determined to within 0. 5 eV without the need for spin polarization, and pseudopotentials containing the core hole were only slightly more accurate than the Z+1 approximation. Core level shifts can be predicted from ground state eigenvalue differences only when comparing environments of comparable electronegativity. Such is the case for the O- K edge, but not the Si L edge at $Si/SiO_2$ interfaces in nanotransistors.