# Charge-transfer effect in hard x-ray 1$s$ and 2$p$ photoemission spectra: LDA+DMFT and cluster-model analysis

## TL;DR

This paper investigates charge-transfer effects in hard x-ray 1s and 2p photoemission spectra of transition metal oxides using LDA+DMFT and cluster-model analysis, revealing the sensitivity of 1s spectra to chemical bonding and screening.

## Contribution

It introduces an ab-initio LDA+DMFT approach to accurately analyze charge-transfer effects in core-level XPS, validated against experimental spectra.

## Key findings

- 1s XPS is a sensitive probe of chemical bonding and charge-transfer screening.
- LDA+DMFT accurately reproduces experimental charge-transfer effects.
- 1s spectra provide complementary information to 2p spectra.

## Abstract

We study $1s$ and $2p$ hard x-ray photoemission spectra (XPS) in a series of late transition metal oxides: Fe$_2$O$_3$ (3$d^{5}$), FeTiO$_3$ (3$d^{6}$), CoO (3$d^{7}$) and NiO (3$d^{8}$). The experimental spectra are analyzed with two theoretical approaches: the MO$_6$ cluster model and the local density approximation (LDA) + dynamical mean-field theory (DMFT). Owing to the absence of the core-valence multiplets and spin-orbit coupling, 1$s$ XPS is found to be a sensitive probe of chemical bonding and nonlocal charge-transfer screening, providing complementary information to 2$p$ XPS. The 1$s$ XPS spectra are used to assess the accuracy of the $ab$-initio LDA+DMFT approach, developed recently to study the material-specific charge-transfer effects in core-level XPS.