First-principles Interpretations of Near-edge X-ray Absorption and Inelastic X-ray Scattering at K-edges in Condensed Phases: the Role of Static and Dynamical and Symmetry-breaking
The increasing application of synchrotron light sources to characterization of complex materials under working conditions creates more demand for accurate, first-principles approaches to interpret spectroscopy. In this talk, we address the use of constrained excited-state density functional theory (DFT) in approximating 1s core-excited states of atoms in condensed phase materials and the subsequent simulation of X-ray absorption spectra with predictive accuracy. Our approach describes the core-excited state with explicit inclusion of both the excited electron and Core-Hole (XCH).
We highlight specific details that enable us to accurately reproduce absorption onsets with 0.1-0.2 eV accuracy and to include experimental sampling of dynamical degrees of freedom via first-principles molecular dynamics. Applications will be presented to materials of relevance to electrical energy storage and gas separations. Particular emphasis will be placed on developing a keen understanding of new spectral features that arise purely from static or dynamical symmetry-breaking in the neighborhood of the core-excited atom and how this knowledge can be exploited to design future in situ experiments on materials in operando.