Phonons in layered compounds

Layer compounds exhibit highly anisotropic structural and elastic properties. They are characterized by rather rigid layers, loosely stacked together perpendicular to each other. Accordingly, the phonon dispersion of layered compounds are characterized by low lying inter -layer modes and high-frequency intra -layer modes. Intercalation compounds composed of a regular sequence of host and guest layers provide a playground for the investigation of the layer lattice dynamics by systematically changing the guest species and the number of guest layers per unit cell. In this contribution a brief overview of some characteristic features of the lattice dynamics of layered compounds is provided.