X-Ray Absorption Fingerprints from Cs Atoms in Cs3Sb

X-ray absorption spectroscopy represents a valuable characterization tool for complex materials like multialkali antimonides. The interpretation of such experimental results greatly benefits from state-of-the-art theoretical references. In a first-principles work based on density-functional theory and many-body perturbation theory, the fingerprints of X-ray absorption near-edge structure (XANES) of Cs3Sb from the Cs K- and L-3-edge are unraveled. From the electronic structure and the orbital character of the conduction bands, the contributions to the XANES spectra from the two inequivalent Cs atoms in the adopted stoichiometric unit cell are analyzed. The predominant weight of Cs s- and d-electrons in the unoccupied region anticipates the relatively high signal yielded by the L-3-edge. Clear atomic signatures, in the form of a pronounced excitonic peak, are visible in the Cs K-edge spectra. In the XANES from the L-3-edge, both Cs atoms yield similar contributions, which are yet distinguishable in the presented calculations. Quantitative analysis enabled by the adopted methodology reveals that electron-hole correlation effects manifest themselves mainly through a redistribution of the oscillator strength to lower energies, whereas exciton binding energies are on the order of a few hundred meV.