Phonon dispersion and its implications towards thermoelectricity

Phonons are quasi-particles that aid in the transfer of heat within solids, and their dynamics are essential for deriving various thermal properties like thermal expansion, specific heat, and lattice thermal conductivity. Materials exhibiting constituent elements with competitive atomic masses are responsible for the interaction between phonon modes, as supported by the phonon dispersion of simple structural forms [1] to the complex ones like skutterudites [2]. Highly interactive phonon modes affect thermal transport and eventually result in low lattice thermal conductivity, a vital thermoelectric coefficient. The phonon dispersion of various materials falling in the family of layered oxy-chalcogenides [3], metal-organic hybrid perovskites like CH₃NH₃SnI₃ [4] and oxides such as CsAgO [5] have been addressed here in light of significance of structural geometry upon lattice thermal transport. The comparative analysis of phonon dispersion for opted materials suggests that low-frequency phonon modes are highly interacting especially in CH₃NH₃SnI₃ and CsAgO, which is a promising sign for low lattice thermal transport in these materials and enable them viable candidates for good thermoelectrics.