Deformation at the limit of elastic stability

We describe mechanical behavior in a defect-free world and find many familiar features. Among them: (1) in a world governed by elastic stability, the common bcc metals would exhibit “pencil glide” in 〈1 1 1〉 and would cleave on {1 0 0}. They would be “conditionally brittle” at low temperature; (2) the common fcc metals would glide on {1 1 1} and would not cleave under simple tensile loads. They would be ductile at low temperature; (3) the maximum values of the nanohardness of simple metals would be very nearly what they are.