We present a study of the elastic and plastic behavior of nanoporous gold in
compression, focusing on molecular dynamics simulation and inspecting
experimental data for verification. Both approaches agree on an anomalously
high elastic compliance in the early stages of deformation, along with a quasi
immediate onset of plastic yielding even at the smallest load. Already before
the first loading, the material undergoes spontaneous plastic deformation under
the action of the capillary forces, requiring no external load. Plastic
deformation under compressive load is accompanied by dislocation storage and
dislocation interaction, along with strong strain hardening.
Dislocation-starvation scenarios are not supported by our results. The
stiffness increases during deformation, but never approaches the prediction by
the relevant Gibson-Ashby scaling law. Microstructural disorder affects the
plastic deformation behavior and surface excess elasticity might modify elastic
response, yet we relate the anomalous compliance and the immediate yield onset
to an atomistic origin: the large surface-induced prestress induces elastic
shear that brings some regions in the material close to the shear instability
of the generalized stacking fault energy curve. These regions are elastically
highly compliant and plastically weak