Phonon relaxation due to anharmonism and central peak in structural phase transitions. II. Soft optic modes in uniaxial ferroelectrics and soft acoustic modes in cubic crystals

In the mode—mode coupling approximation the critical exponents (CE) are calculated for the dampings and frequency shifts of soft optic modes and acoustic phonons (in uniaxial ferroelectrics) and for the dampings of soft acoustic phonons (in cubic crystals) in the structural transition point. The CE are traced back to the anharmonic interaction (of all orders) of soft phonons with the intrinsic dynamic central peak of any nature. [Russion Text Ignored]