Planar fault energies of copper at large strain: A density functional theory study

We present density functional theory calculations of the extrinsic stacking fault energy γ_esf, twin fault energy γ_tf, and unstable stacking fault energy γ_usf of copper under large strains, up to ± 10%. The calculated values of γ_esf, γ_tf, and γ_usf for unstrained Cu are 41.8 mJ/m², 20.2 mJ/m², and 163.4 mJ/m², respectively, in good agreement with experimental data and theoretical results. Four different types of strains are applied: (i) volumetric strain; (ii) uniaxial strain perpendicular to the fault plane; (III) uniaxial strains parallel to the fault plane; and (iv) shear strains across the fault planes. We find that γ_esf, γ_tf, and γ_usf are strongly dependent on the magnitude and type of strain, challenging the common conception that they are constant material properties. The predicted strong strain dependencies provide useful insight into the deformation mechanisms of copper under high pressure and shock conditions and provide essential data to improve current Cu empirical potentials.