Electronic fluctuations, cation clustering, and ionic dynamics in molten silver iodide.

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Chemistry

Background:

• Molten salts are high-temperature ionic liquids crucial for energy storage, metallurgy, and nuclear applications.
• Understanding electronic polarization and its fluctuations is vital for predicting molten salt behavior and designing new materials.

Purpose of the Study:

• To investigate the role of electronic fluctuations in the structure and dynamics of molten silver iodide (AgI).
• To compare the accuracy of density functional theory (DFT), a universal machine learning model (Orb), and an empirical pairwise model in capturing these effects.

Main Methods:

• Simulations using density functional theory (DFT).
• Application of a universal neural network potential (Orb).
• Utilizing a classical, empirical pairwise model for interionic interactions.

Main Results:

• Iodide ion polarizability screens cation-cation interactions, causing cation clustering.
• Directional polarization fluctuations of iodide ions enhance silver ion diffusion, creating dynamic asymmetry.
• The Orb model accurately reproduces DFT results, capturing many-body polarization effects, while the empirical model fails.

Conclusions:

• Electronic fluctuations, particularly iodide polarization, are critical for molten AgI structure and dynamics, especially cation diffusion.
• The universal neural network potential (Orb) shows high fidelity in simulating complex polarization phenomena.
• Findings link liquid-state ionic dynamics to mechanisms in superionic solids, guiding future electrolyte design.