Icosahedral short-range order in amorphous alloys

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Amorphous solids lack long-range crystalline order but can exhibit local structural ordering.
• Understanding short-range order (SRO) is crucial for predicting material properties and behavior.
• Icosahedral SRO is a common motif in metallic glasses, influencing their stability and transformation pathways.

Purpose of the Study:

• To characterize the presence and extent of icosahedral short-range order in amorphous alloys.
• To investigate if icosahedral SRO persists in amorphous alloys that do not form quasicrystalline phases upon annealing.
• To utilize advanced spectroscopic and simulation techniques for probing local atomic environments.

Main Methods:

• Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy to probe local atomic arrangements.
• X-ray Absorption Near-Edge Structure (XANES) spectroscopy to determine electronic and local structural properties.
• Reverse Monte Carlo (RMC) simulations to model and interpret the experimental data, reconstructing the atomic structure.

Main Results:

• The study confirmed the significant presence of icosahedral short-range order in the amorphous Ni-Ag alloy.
• This icosahedral SRO was detected even though the alloy does not crystallize into a quasicrystalline phase.
• Analysis revealed that topological local order is a pronounced feature of this amorphous system.

Conclusions:

• Icosahedral short-range order is a fundamental characteristic of certain amorphous alloys, independent of their crystallization behavior.
• Local environment probes, combined with RMC simulations, are effective tools for identifying and quantifying complex SRO in disordered materials.
• The findings contribute to a deeper understanding of the structure-property relationships in amorphous alloys.