Softening point Soft” mode

In general, the driving force of the phase transition is a soft mode [157]. A vibrational lattice mode with a given phase difference between the unit cells inoeases its amplitude, and tbc vibrational frequency shifts toward zero as the temperature approaches the tran-sitioo point. This h considered to be caused by the softening of intennolecular interne-... 

Second-order phase transitions also show up via the critical slowing down of the critical fluctuations (Hohenberg and Halperin, 1977). In structural phase transitions, one speaks about soft phonon modes (Blinc and Zeks, 1974 Bruce and Cowley, 1981) in isotropic magnets, magnon modes soften as T approaches Tc from below near the critical point of mixtures the interdiffusion is slowed down etc. This critical behavior of the dynamics of fluctuations is characterized by a dynamic critical exponent z one expects that some characteristic time r exists which diverges as T - TCl... 

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