On the ab initio calculation of CVV Auger spectra in closed-shell systems

TL;DR

This paper introduces an ab initio method based on DFT to accurately calculate CVV Auger spectra in closed-shell systems, accounting for complex interactions and non-sphericity effects, validated on Zn and Cu metals.

Contribution

The paper develops a first-principles approach to compute CVV Auger spectra, incorporating detailed electronic effects and providing benchmark results for metals.

Findings

Accurately predicts Auger peaks within 2 eV of experimental data for Zn and Cu.

Highlights the importance of non-sphericity and spin-orbit effects in spectra calculations.

Identifies challenges in estimating hole-hole interactions in systems with broad valence bands.

Abstract

We propose an ab initio method to evaluate the core-valence-valence (CVV) Auger spectrum of systems with filled valence bands. The method is based on the Cini-Sawatzky theory, and aims at estimating the parameters by first-principles calculations in the framework of density-functional theory (DFT). Photoemission energies and the interaction energy for the two holes in the final state are evaluated by performing DFT simulations for the system with varied population of electronic levels. Transition matrix elements are taken from atomic results. The approach takes into account the non-sphericity of the density of states of the emitting atom, spin-orbit interaction in core and valence, and non quadratic terms in the total energy expansion with respect to fractional occupation numbers. It is tested on two benchmark systems, Zn and Cu metals, leading in both cases to L23M45M45 Auger peaks within 2 eV from the experimental ones. Detailed analysis is presented on the relative weight of the various contributions considered in our method, providing the basis for future development. Especially problematic is the evaluation of the hole-hole interaction for systems with broad valence bands: our method underestimates its value in Cu, while we obtain excellent results for this quantity in Zn.