LATTICE ANOMALY AND DYNAMICS OF CUGEO3

We have performed neutron scattering on both single crystal and powder samples of spin-Peierls system CuGeO3. Below the transition temperatu re T-sp, we found spontaneous strains in all crystal axes. Temperature dependence of the lattice constants and phonon density of states chan ge drastically well above T-sp, which is apparently linked with the tr ansition. Thus, we concluded that inherent structural instability make s a favorable condition for the SP transition and also continuous tran sformation affects magnetic behavior above T-sp.