Molecular Spin Crossover Materials: Review of the Lattice Dynamical Properties

The lattice dynamical aspects of the spin crossover phenomenon in molecular solids—displaying intricate couplings between the electronic spin state of the molecules and the lattice properties—are reviewed. Emphasis is on experimental and theoretical approaches giving access to the vibrational spectra and to key properties, such as the heat capacity, vibrational entropy and enthalpy, lattice rigidity, elastic constants, and elastic interactions. Recent results in relation to surface and finite size effects as well as with ultrafast out‐of‐equilibrium phenomena are also covered.