Effective Mass of a Migrating Interface

TL;DR

This paper demonstrates that migrating interfaces in materials exhibit inertial behavior under high-frequency loading and introduces a method to measure their effective mass, impacting models of interface kinetics.

Contribution

It provides a quantitative method to determine the effective mass of migrating interfaces, challenging the common assumption of massless interfaces in kinetic models.

Findings

Effective mass correlates with atomic participation in migration.

Inertial effects are significant at high frequencies.

Reassessment of interface kinetic theories considering inertia.

Abstract

Interfaces in materials are often treated as massless geometric boundaries, and many kinetic models adopt an overdamped assumption. In this Letter, we show that grain boundaries exhibit inertial behavior under high-frequency oscillatory loading and introduce a quantitative method to determine their effective mass from the phase lag between the applied force and interface velocity. The measured effective mass correlates with the mass of atoms participating in interface migration. Using this advance, we reassess prevailing theories and identify regimes where the inertial term materially affects interfacial kinetics, particularly at high frequencies relevant to thermal fluctuations. These results motivate incorporating an effective mass into kinetic descriptions, providing a clearer basis for modeling and interpreting interface migration.