Investigation on a high-T-c superconductor, La1.85Sr0.15CuO4, was perf
ormed in the wide range of Q-E space by means of neutron scattering an
d synchrotron radiation. The structure as well as the phonon dynamics
showed a clear evolution at T-c. We found a spontaneous strain and pho
non softening, which proves a strong coupling between lattice and supe
rconductivity.