Odd-parity mode frequency and lifetime.
For sufficiently small amplitude, the frequency of the mode lies close
to the optic plane wave band. With increasing amplitude the mode
becomes sufficiently localized so that both the ac and the dc
components are concentrated in the vicinity of the central
particle. The ac vibrational pattern of such a gap mode is displayed
in the figure. When the amplitude of the central particle becomes
even larger, A/d > 0.2,
its frequency crosses into the acoustic band and its
eigenvector converts to a band mode .
The frequency of an anharmonic gap mode in a diatomic lattice as a
function of normalized amplitude, A/d. The
odd-parity mode is centered at the light atom. The molecular dynamics
simulation results are represented by squares while the analytic
results are given by the solid line. The triatomic molecule
approximation is represented by the dashed line.
 S. A. Kiselev, S. R. Bickham and A. J. Sievers, Phys. Lett. A
184, 255 (1993).
Last modified: August 10, 1997