I want to know the answer to the following question:
What term describes the vibrational lattice mode that turns to 0 frequency at the change?
All the background I'm provided with is that "An example is ferroelectric materials, where the change from a paraelectric to a ferroelectric state occurs at the Curie temperature and is related to a change from the high-symmetry paraelectric state to the lower symmetry ferroelectic state, accompanied by a so-called soft phonon mode, a vibrational lattice mode that goes to zero frequency at the transition.". Is that enough to answer the question?
Answer: yes