Adlayer core-level shifts of random metal overlayers on transition-metal substrates

TL;DR

This study uses density functional theory to analyze core-level shifts in random metal overlayers on transition-metal substrates, highlighting the importance of screening effects and alloy composition on surface chemistry.

Contribution

It provides a detailed theoretical analysis of core-level shifts in alloy overlayers, emphasizing the role of screening effects and alloy composition, which advances understanding of surface reactivity.

Findings

Final-state screening effects are crucial for interpreting core-level shifts.

Alloy composition significantly influences inter- and intra-atomic screening.

Changes in screening upon alloying affect surface chemical reactivity.

Abstract

We calculate the difference of the ionization energies of a core-electron of a surface alloy, i.e., a B-atom in a A_(1-x) B_x overlayer on a fcc-B(001)-substrate, and a core-electron of the clean fcc-B(001) surface using density-functional-theory. We analyze the initial-state contributions and the screening effects induced by the core hole, and study the influence of the alloy composition for a number of noble metal-transition metal systems. Data are presented for Cu_(1-x)Pd_x/Pd(001), Ag_(1-x) Pd_x/Pd(001), Pd_(1-x) Cu_x/Cu(001), and Pd_(1-x) Ag_x/Ag(001), changing x from 0 to 100 %. Our analysis clearly indicates the importance of final-state screening effects for the interpretation of measured core-level shifts. Calculated deviations from the initial-state trends are explained in terms of the change of inter- and intra-atomic screening upon alloying. A possible role of alloying on the chemical reactivity of metal surfaces is discussed.