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 al uminum. and copper using pseudopotential density functional theory within t he local density approximation. Structural relaxations orthogonal to the ap plied shear significantly reduce the values of ideal shear strength, result ing 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 deg ree, this can be explained using experimentally measured third-order elasti c constants. (C) 2001 Elsevier Science B.V. All rights reserved.