Free energy generalization of the Peierls potential in iron

TL;DR

This paper extends the Peierls potential in bcc iron to include free energy considerations, revealing how stress and temperature influence dislocation behavior and plasticity.

Contribution

It introduces a thermodynamic extension of the Peierls potential for bcc Fe using thermodynamic integration, accounting for stress and temperature effects.

Findings

Critical stress vanishes at 700K.

Peierls free energy path computed as a function of stress and temperature.

Provides insights into plastic behavior in the athermal limit.

Abstract

In body-centered cubic (bcc) crystals, ${1}{2}111$ screw dislocations exhibit high intrinsic lattice friction as a consequence of their non-planar core structure, which results in a periodic energy landscape known as the Peierls potential, $U_P$. The main features determining plastic flow, including its stress and temperature dependences, can be derived directly from this potential, hence its importance. In this Letter, we use thermodynamic integration to provide a full thermodynamic extension of $U_P$ for bcc Fe. We compute the Peierls free energy path as a function of stress and temperature and show that the critical stress vanishes at 700K, supplying the qualitative elements that explain plastic behavior in the athermal limit.