  A one-dimensional system of masses with nearest-neighbor interactions and
periodic boundary conditions is used to study mode decay and ergodicity in
nonlinear, disordered systems. The system is given an initial periodic
displacement, and the total system energy within a specific frequency channel
is measured as a function of time. Results indicate that the rate of mode decay
at early times increases when impurities are added. However, for long times the
rate of mode decay decreases with increasing impurity mass and impurity
concentration. This behavior at long times can be explained by Anderson
localization effects and the nonergodic response of the system.
