Impact of intrinsic localized modes of atomic motion on materials properties

TL;DR

This paper investigates how intrinsic localized modes (ILMs) in atomic motion affect various properties of materials like uranium and sodium iodide, revealing their influence on thermal, mechanical, and transport behaviors.

Contribution

It provides new insights into the role of ILMs in modifying material properties and suggests potential applications in thermoelectrics and understanding phase transformations.

Findings

ILMs enhance thermal expansion and induce anisotropy.

ILMs suppress lattice thermal conductivity above activation temperature.

ILMs influence diffusion, conductivity, and fracture behavior.

Abstract

Recent neutron and x-ray scattering measurements show intrinsic localized modes (ILMs) in metallic uranium and ionic sodium iodide. Here, the role ILMs play in the behavior of these materials is examined. With the thermal activation of ILMs, thermal expansion is enhanced, made more anisotropic, and, at a microscopic level, becomes inhomogeneous. Interstitial diffusion, ionic conductivity, the annealing rate of radiation damage, and void growth are all influenced by ILMs. The lattice thermal conductivity is suppressed above the ILM activation temperature while no impact is observed in the electrical conductivity. This complement of transport properties suggests that ILMs could improve thermoelectric performance. Ramifications also include thermal ratcheting, a transition from brittle to ductile fracture, and possibly a phase transformation in uranium.