Tiny nanodiamonds bend, not break, due to a hidden elastic layer

A custom electron microscope shows nanodiamonds deform elastically under pressure because a relatively weak bond between their surface layer and core, amplified by a large surface-to-core ratio, concentrates strain in an interfacial zone that absorbs the shock. Smaller diamonds (around 4 nm) are about 30% more stretchy than larger ones (around 13 nm), illustrating size-dependent elasticity and offering practical knobs for nanoscale devices like nanomechanical resonators and quantum sensors.