Gas-phase valence-electron photoemission spectroscopy using density functional theory.

We present a tutorial overview of the simulation of gas-phase valence-electron photoemission spectra using density functional theory (DFT), emphasizing both fundamental considerations and practical applications, and making appropriate links between the two. We explain how an elementary quantum mechanics view of photoemission couples naturally to a many-body perturbation theory view. We discuss a rigorous approach to photoemission within the framework of time-dependent DFT. Then we focus our attention on ground-state DFT. We clarify the extent to which it can be used to mimic many-body perturbation theory in principle, and then provide a detailed discussion of the accuracy one can and cannot expect in practice with various approximate DFT forms.