The effect of normal stress on stacking fault energy in face-centered cubic metals

TL;DR

This study uses DFT calculations to analyze how normal stress influences stacking fault energies in six FCC metals, revealing significant effects and limitations of current interatomic potentials.

Contribution

It provides detailed DFT insights into stress effects on SF energies in FCC metals and evaluates the accuracy of classical and machine-learning potentials.

Findings

Normal compression increases SF energies in all six metals.

Normal tension decreases SF energies.

Many potentials fail to accurately predict stress effects on SF energy.

Abstract

Plastic deformation and fracture of FCC metals involve the formation of stable or unstable stacking faults (SFs) on (111) plane. Examples include dislocation cross-slip and dislocation nucleation at interfaces and near crack tips. The stress component normal to (111) plane can strongly affect the SF energy when the stress magnitude reaches several to tens of GPa. We conduct a series of DFT calculations of SF energies in six FCC metals: Al, Ni, Cu, Ag, Au, and Pt. The results show that normal compression significantly increases the stable and unstable SF energies in all six metals, while normal tension decreases them. The SF formation is accompanied by inelastic expansion in the normal direction. The DFT calculations are compared with predictions of several representative classical and machine-learning interatomic potentials. Many potentials fail to capture the correct stress effect on the SF energy, often predicting trends opposite to the DFT calculations. Possible ways to improve the ability of potentials to represent the stress effect on SF energy are discussed.