Ordering mechanism and dynamics of relaxor ferroelectrics

It is shown that the validity conditions of symmetry adapted random-bond-ra ndom-field model with rotation symmetry of local order parameter in the sys tem of nanoscale polar domains in relaxors are fulfilled due to increasing of dispersion of soft TO-phonon. The latter is due to interaction of quasil ocal modes of nanoscale domains with soft TO-phonons. As a result, long-wav e contribution to domain-domain indirect interaction (DDII) and mean field effect are strongly increased. The quasi-rotation symmetry can be fulfilled due to intradomain disorder effects with high degree of quasi-degeneracy o f orientation states of domain local order parameter. Local configuration i nstabilities of the first and of the second order for nanoscale domains are appeared due to softening of domain quasilocal modes essentially renormali zed by dipole-dipole DDII. Compensation of extra-charge of nanoscale domain s in relaxors due to ferroelectrically ordered charge transfer vibronic exc itons in each cell with simultaneous domain polarization appearance is subs tantiated.