A comprehensive study of thermal conductivity and infrared dielectric properties of PbTe

The low thermal conductivity (κ) of lead telluride (PbTe) has attracted significant attention due to its role as a representative mid-temperature thermoelectric material. Although numerous studies have explored its κ, conventional approaches such as density functional perturbation theory and the quasi-harmonic approximation fall short in fully accounting for temperature-induced phonon renormalization in PbTe. Thus, a more advanced method capable of accurately capturing these temperature effects is necessary. In this study, we combine ab initio molecular dynamics with the temperature-dependent effective potential method to precisely model the temperature-dependent phonon spectrum. Notably, we successfully reproduce the anomalous hardening of the transverse optical (TO) mode at the Γ point with increasing temperature. Using the renormalized phonons, we calculate κ values that align closely with experimental data over a wide temperature range and elucidate the underlying mechanism of low κ in PbTe. The strong anharmonic scatterings of the TO modes are identified as the primary causes. Furthermore, by leveraging accurately obtained phonon parameters, we compute the dielectric constant of PbTe and establish a numerical relationship between its dielectric response and thermal transport properties. We predict the temperature-dependent reflectivity of PbTe in the infrared (IR) region, uncovering a pronounced reflectivity peak (above 150 μm) in the far-IR range. This finding offers new perspectives for the multifunctional design of PbTe in optoelectronic, thermoelectric, and terahertz applications.