First-principles calculations of grain boundary theoretical shear strength using transition state finding to determine generalized gamma surface cross sections

We present a first-principles calculation of the theoretical shear strength of the AlSigma3(11 (2) over bar) tilt boundary. Here we replace the usual gamma surface (defined by rigid atomic translations parallel to the boundary) by a generalized gamma surface that includes complex cooperative atomic motions occurring at the grain boundary during shear. Transition-state-finding techniques are well suited for calculations of generalized gamma-surface cross sections. The transition states, saddles on the gamma surface, occur during grain-boundary sliding and at grain-boundary dislocations.