Adiabatic theory of off-center vibronic polarons: Local dynamics on a   planar lattice
  We review basic theoretical concepts and developments regarding the local and itinerant properties of off-center vibronic polarons in crystals. These include the electron self-trapping and the local rotation of the species on a square planar lattice. Phase transitions within the gas of vibronic small polarons are also discussed. 
M. Georgiev