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Updated: Jul 6, 2026

Predicting Catalyst Extrudate Breakage Based on the Modulus of Rupture
Published on: May 13, 2018
Origin of brittle cleavage in iridium
Marc J Cawkwell1, Duc Nguyen-Manh, Christopher Woodward
1Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104-6202, USA. cawkwell@seas.upenn.edu
Abstract:
Iridium is unique among the face-centered cubic metals in that it undergoes brittle cleavage after a period of plastic deformation under tensile stress. Atomistic simulation using a quantum-mechanically derived bond-order potential shows that in iridium, two core structures for the screw dislocation are possible: a glissile planar core and a metastable nonplanar core. Transformation between the two core structures is athermal and leads to exceptionally high rates of cross slip during plastic deformation. Associated with this athermal cross slip is an exponential increase in the dislocation density and strong work hardening from which brittle cleavage is a natural consequence.
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