Quantitative description of short-range order and its influence on the electronic structure in Ag-Pd alloys

TL;DR

This study quantifies how short-range atomic order influences the electronic structure in Ag-Pd alloys using advanced theoretical methods, revealing spectral features that can be observed experimentally.

Contribution

It introduces a parameter to quantify short-range order effects on electronic structure using the Korringa-Kohn-Rostoker method with non-local CPA.

Findings

Spectral features vary with SRO across the valence band energy range.

Changes in SRO affect the density of states and spectroscopic measurements.

The model system covers different alloy compositions and SRO states.

Abstract

We investigate the effect of short-range order (SRO) on the electronic structure in alloys from the theoretical point of view using density of states (DOS) data. In particular, the interaction between the atoms at different lattice sites is affected by chemical disorder, which in turn is reflected in the fine structure of the DOS and, hence, in the outcome of spectroscopic measurements. We aim at quantifying the degree of potential SRO with a proper parameter. The theoretical modeling is done with the Korringa-Kohn-Rostoker Green's function method. Therein, the extended multi-sublattice non-local coherent potential approximation is used to include SRO. As a model system, we use the binary solid solution Ag$_c$Pd$_{1-c}$ at three representative concentrations $c=0.25$, $0.5$ and $0.75$. The degree of SRO is varied from local ordering to local segregation through an intermediate completely uncorrelated state. We observe some pronounced features, which change over the whole energy range of the valence bands as a function of SRO in the alloy. These spectral variations should be traceable in modern photoemission experiments.