It always moves faster than plane waves. The above applet allows you to watch propagating solitons in the lattice of 15 particles with fixed boundaries. The evolution of the chain is calculated by the molecular-dynamics technique. You can also see non-destructive collisions of two sharp solitons . The time is shown in units of the shortest period of small amplitude plane wave vibrations, .
Energy is shown in arbitrary units.
The kinetic energy of the particle and the potential energy of the bond are shown as the red and the yellow bars, respectively. If you wait for a while you will see a power spectrum of the particles' vibrations. It will be shown in the left panel. As the time of the evolution goes the spectrum resolution improves. The frequency unit is the maximal plane wave frequency, .