Strongly Non-Arrhenius Self-Interstitial Diffusion in Vanadium

TL;DR

This study investigates the diffusion behavior of self-interstitial atoms in vanadium, revealing a transition from non-Arrhenius to Arrhenius kinetics with increasing temperature, driven by changes in diffusion mechanisms.

Contribution

It provides new insights into the temperature-dependent diffusion mechanisms of SIAs in vanadium, highlighting the breakdown of Arrhenius behavior at high temperatures.

Findings

Diffusion is one-dimensional at low temperatures.

Diffusion becomes isotropic at higher temperatures due to rotation.

Diffusivity transitions from Arrhenius to linear with temperature above 600 K.

Abstract

We study diffusion of self-interstitial atoms (SIAs) in vanadium via molecular dynamics simulations. The <111>-split interstitials are observed to diffuse one-dimensionally at low temperature, but rotate into other <111> directions as the temperature is increased. The SIA diffusion is highly non-Arrhenius. At T<600 K, this behavior arises from temperature-dependent correlations. At T>600 K, the Arrhenius expression for thermally activated diffusion breaks down when the migration barriers become small compared to the thermal energy. This leads to Arrhenius diffusion kinetics at low T and diffusivity proportional to temperature at high T.