What is a clear definition of vibrons? Vibrons are localized Phonons and I need more information about them. It is somewhat vague to me. Can you give some references, please?
The term vibron isn't a standard accepted word in solid state physics. It's simply a synonym of a phonon, which was probably coined before phonon.
As far as localization is concerned, phonons can be localized too. For example, in a crystal lattice, the vibrations can propagate throughout the crystal, or there can be vibrations in only a small localized part of the crystal. In both the cases, the resulting vibrational quanta can be called a phonon.