XPS core-level chemical shift by ab initio many-body theory

TL;DR

This paper compares various ab initio theoretical methods to accurately predict chemical shifts in X-ray photoemission spectroscopy, identifying electrostatics as the key physical factor behind the shifts.

Contribution

It systematically benchmarks different many-body theories against experimental data and decomposes chemical shifts to reveal their physical origins.

Findings

GW approximation yields accurate chemical shift predictions

Decomposition shows electrostatics as the main contributor

Benchmarking against experiments validates the theoretical approaches

Abstract

X-ray photoemission spectroscopy (XPS) provides direct information on the atomic composition and stoichiometry by measuring core electron binding energies. Moreover, according to the shift of the binding energy, so-called chemical shift, the precise chemical type of bonds can be inferred, which brings additional information on the local structure. In this work, we present a theoretical study of the chemical shift firstly by comparing different theories, from Hartree-Fock (HF) and density-functional theory (DFT) to many-body perturbation theory (MBPT) approaches like the GW approximation and its static version (COHSEX). The accuracy of each theory is assessed by benchmarking against the experiment on the chemical shift of the carbon 1s electron in a set of molecules. More importantly, by decomposing the chemical shift into different contributions according to terms in the total Hamiltonian, the physical origin of the chemical shift is identified as classical electrostatics.