  We explore the malleability of ultra-small metal nanoparticles by means of ab
initio calculations. It is revealed that, when strained, such nanoparticles
exhibit complex behavior, including bifurcation between slow and fast quakes of
their atomic structure, despite being few-body systems. We show the bifurcation
to arise from the collapse of the nanoparticle's stiffness and a broken soft
mode symmetry, and that whether a slow or fast quake occurs can be controlled
by varying the amplitude of the externally applied strains. We predict that
while energy is released abruptly in a fast quake, surprisingly, it continues
to build up during a slow quake and that, in common with slow-slip geological
earthquakes, the slow nanoparticle quake is a silent precursor to a fast
"seismic" quake. We show that electrical conductance and force measurements can
detect and distinguish between slow and fast quakes, opening the way for
experiments and potential applications of these phenomena.
