Lattice charge models and core level shifts in disordered alloys

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Core level binding energies are influenced by charge distributions and screening effects.
• Existing models for net atomic charges in alloys have limitations, particularly for multi-component systems.

Purpose of the Study:

• To generalize the linear charge model for alloys using the charge-excess functional model (CEFM).
• To derive analytical expressions for physical quantities like Madelung energy and disorder broadening.
• To apply the model to understand core level binding energy shifts in specific alloy systems.

Main Methods:

• Derivation of the CEFM energy function and analysis of its approximations.
• Investigation of a specific CEFM case with uniform local interaction strengths.
• Determination of model parameters ('geometric factors') and derivation of analytical expressions for physical quantities.

Main Results:

• The CEFM generalizes the linear charge model for alloys with more than two species.
• Charge screening universality increases with local interaction strength.
• Madelung energy and disorder broadening in ternary alloys are maximized at specific compositions.
• Effective radii for valence electron charge transfer in CuPd and CuZn alloys were deduced.

Conclusions:

• The CEFM provides a framework for rationalizing disorder broadening in alloys.
• Disorder broadening arises from an interplay of Madelung and intra-atomic electrostatic potentials.
• Deduced effective radii are consistent across different elements and systems, aiding X-ray photoelectron spectroscopy analysis.