The non-linear elastic behavior and ideal shear strength of Al and Cu

We present recent ab initio calculations of the ideal shear strengths of aluminum and copper using pseudopotential density functional theory within the local density approximation. Structural relaxations orthogonal to the applied shear significantly reduce the values of ideal shear strength, resulting in strengths of 8–9% of the shear modulus for both Al and Cu. However, the geometry of the relaxations in Al and Cu is very different. To some degree, this can be explained using experimentally measured third-order elastic constants.