To conclude, we have build a model Hamiltonian for the orientational disorder in the hybrid organic-inorganic ferroelectric material TMCMCdCl 3 fitted to energies calculated from first principles both with and without inclusion of vibrational contributions. We show that the ferroelectric-to-paraelectric phase transition temperature can be quantitatively reproduced when vibrational entropic contributions are included, highlighting the importance of the interplay between vibrational and configurational degrees of freedom for soft and flexible crystalline materials.