  Dissipation from harmonic energy eigenstates is used to characterize energy
transport in binary isotopically disordered (BID) Fermi-Pasta-Ulam (FPU-beta)
chains. Using a continuum analog for the corresponding harmonic portion of the
Hamiltonian, the time-independent wave amplitude is calculated for a plane wave
having wavelength \lambda that is incident upon the disordered section, and the
solution is mapped onto the discrete chain. Due to Anderson localization,
energy is initially localized near the incident end of the chain, and in the
absence of anharmonicity the wave amplitude is stationary in time. For
sufficient anharmonicity, however, mode transitions lead to dissipation. Energy
transport along the chain is quantified using both the second moment M of the
site energy, and the number of masses contributing to transport, which was
estimated from the localization parameter. Over the time scales studied, M
increased linearly in time, yielding an effective transport coefficient G. At
low and intermediate impurity concentration, G(c) can be characterized by a
competition between the rate of mode transitions and the time for energy to
propagate a distance equal to the localization length \xi. At the highest
concentrations (1.6 \le c\lambda \le 16.0), there is significant mode
transition suppression in BID systems, and the transport coefficient G(c)
becomes proportional to \xi(c).
