Ideal strengths of bcc metals

We present ab initio ideal strength calculations in body-centered cubic (bcc) tungsten for ‘pencil-glide’ slip on {110}, {112}, and {123} planes and for the {100} cleavage strength. We use these results to analyze the tensile and shear strengths of other bcc metals. In all bcc metals, the minimum shear strength on any plane containing 〈111〉 is ≈0.11/S〈111〉, where S〈111〉 is the elastic compliance for any shear in a 〈111〉 direction. The ideal cleavage strength on {100} for many bcc metals is ≈0.083/s11 where s11 is the single crystal elastic compliance. Comparison of the ideal shear and tensile strengths offers a measure of the inherent ductility or brittleness of a material.