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 bee metals, the minimum shear strength on any plane containing <111> is approximate to0.11/S-<111>, where S-<111> is the elastic compliance for any shear in a <111> direction. The ideal cleavage strength on {100} for many bee metals is approximate to0.083/s(11) where s(11) 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. (C) 2001 Elsevier Science B.V. All rights reserved.