  We derive large-amplitude collective equations of motion from the variational
principle for the time-dependent Schroedinger equation. These equations reduce
to the well-known diabatic formulas for vibrational frequencies in the small
amplitude limit. The finite amplitude expression allows departures from
harmonic behavior of giant resonances to be simply estimated. The relative
shift of the second phonon falls with nuclear mass A as A^(-4/3) in the three
modes we consider: monopole, dipole, and quadrupole. Numerically the effect is
very small in heavy nuclei, as was found with other approaches.
