Tuneable Correlated Disorder in Alloys

TL;DR

This study reveals a new form of tunable correlated disorder in alloys caused by crystallographic mismatch, demonstrating strong disorder-phonon coupling and its potential for phonon engineering in functional materials.

Contribution

It introduces a systematic way to study correlated disorder via epitaxial alloy stabilization and combines experimental and computational methods to uncover disorder-phonon interactions.

Findings

Tunable correlated disorder arises from crystallographic mismatch.

Strong disorder-phonon coupling suppresses phonon lifetimes.

Implications for designing materials with tailored phononic properties.

Abstract

Understanding the role of disorder and the correlations that exist within it, is one of the defining challenges in contemporary materials science. However, there are few material systems, devoid of other complex interactions, which can be used to systematically study the effects of crystallographic conflict on correlated disorder. Here, we report extensive diffuse x-ray scattering studies on the epitaxially stabilised alloy $\mbox{U}_{1-x}\mbox{Mo}_x$, showing that a new form of intrinsically tuneable correlated disorder arises from a mismatch between the preferred symmetry of a crystallographic basis and the lattice upon which it is arranged. Furthermore, combining grazing incidence inelastic x-ray scattering and state-of-the-art ab initio molecular dynamics simulations we discover strong disorder-phonon coupling. This breaks global symmetry and dramatically suppresses phonon-lifetimes compared to alloying alone, providing an additional design strategy for phonon engineering. These findings have implications wherever crystallographic conflict can be accommodated and may be exploited in the development of future functional materials.