{110} planar faults in strained bcc metals: Origins and implications of a commonly observed artifact of classical potentials

TL;DR

This study investigates how classical potentials in atomistic simulations can produce artificial planar faults in bcc metals under strain, highlighting the importance of using advanced models like DFT to avoid artifacts.

Contribution

The paper reveals that stable planar faults in strained bcc metals are artifacts of classical potentials and not physical phenomena, emphasizing the need for more sophisticated modeling.

Findings

Classical potentials often show local minima in GSFE under strain, leading to artificial planar faults.

More advanced models like DFT do not exhibit these artifacts, confirming their non-physical nature.

Recommends strain-dependent GSFE as a benchmark for potential development.

Abstract

Large-scale atomistic simulations with classical potentials can provide valuable insights into microscopic deformation mechanisms and defect-defect interactions in materials. Unfortunately, these assets often come with the uncertainty of whether the observed mechanisms are based on realistic physical phenomena or whether they are artifacts of the employed material models. One such example is the often reported occurrence of stable planar faults (PFs) in body-centered cubic (bcc) metals subjected to high strains, e.g., at crack tips or in strained nano-objects. In this paper, we study the strain dependence of the generalized stacking fault energy (GSFE) of {110} planes in various bcc metals with material models of increasing sophistication, i.e., (modified) embedded atom method, angular-dependent, Tersoff, and bond-order potentials as well as density functional theory. We show that under applied tensile strains the GSFE curves of many classical potentials exhibit a local minimum which gives rise to the formation of stable PFs. These PFs do not appear when more sophisticated material models are used and have thus to be regarded as artifacts of the potentials. We demonstrate that the local GSFE minimum is not formed for reasons of symmetry and we recommend including the determination of the strain-dependent (110) GSFE as a benchmark for newly developed potentials.