Structural transformations driven by local disorder at interfaces

TL;DR

This study investigates the atomistic mechanisms of solid-solid phase transformations in tungsten, revealing the role of local disorder at interfaces through advanced simulations, and highlights how interface structure influences transformation dynamics.

Contribution

It introduces a machine learning-based approach combined with metadynamics to explore complex interface structures during phase transformations, uncovering the significance of local disorder.

Findings

Disordered regions at interfaces facilitate atomic rearrangements.

Interface mobility varies with orientation relationships.

Disordered interface regions correlate with transformation mechanisms.

Abstract

Despite the fundamental importance of solid-solid transformations in many technologies, the microscopic mechanisms remain poorly understood. Here, we explore the atomistic mechanisms at the migrating interface during solid-solid phase transformations between the topologically closed-packed A15 and body-centred cubic phase in tungsten. The high energy barriers and slow dynamics associated with this transformation require the application of enhanced molecular sampling approaches. To this end, we performed metadynamics simulations in combination with a path collective variable derived from a machine learning classification of local structural environments, which allows the system to freely sample the complex interface structure. A disordered region of varying width forming at the migrating interface is identified as a key physical descriptor of the transformation mechanisms, facilitating the atomic shuffling and rearrangement necessary for structural transformations. Furthermore, this can directly be linked to the differences in interface mobility for distinct orientation relationships as well as the formation of interfacial ledges during the migration along low-mobility directions.