  Transmission electron microscopy experiments have recently observed gold
metal nanocylinders to thin down in a discrete manner: A kink--a step of order
of one atomic layer--nucleates at one end and then moves along the wire,
leaving a thinner cylinder behind it. In this paper, I show that a similar
thinning process takes place within the nanoscale free-electron model, a
structural and dynamical model of nanowires that treats the
electron-confinement effects exactly while replacing the atomic structure by a
continuum. Electron-shell effects, previously shown to be responsible for the
stability of wires with magic radii, favor the formation of kinks connecting
magic cylinders. A rich kink dynamics including interkink interactions ensues
and is similar to that observed experimentally.
