Dislocations can greatly enhance the figure of merit of thermoelectric materials by prominently reducing thermal conductivity. However, the evolution of phonon modes with different energies when they propagate through a single dislocation is unknown. Here we perform non-equilibrium molecular dynamics simulation to study phonon transport in PbTe crystal with dislocations by excluding boundary scattering and strain coupling effect. The frequency-dependent heat flux, phonon mode analysis, and frequency-dependent phonon mean free paths (MFPs) are presented. The thermal conductivity of PbTe with dislocation density on the order of 10¹⁵ m⁻² is decreased by 62%. We provide solid evidence of strong localization of phonon modes in dislocation sample. Moreover, by comparing the frequency-dependent phonon MFPs between atomistic modeling and traditional theory, it is found that the conventional theories are inadequate to describe the phonon behavior throughout the full phonon spectrum, and large deviation to the well-known semi-classical Matthiessen’s rule is observed. These results provide insightful guidance for the development of PbTe based thermoelectrics and shed light on new routes for enhancing the performance of existing thermoelectrics by incorporating dislocations.

Inorganic semiconductor materials are crucial for modern technologies, but their brittleness and limited processability hinder the development of flexible, wearable, and miniaturized electronics. The recent discovery of room-temperature plasticity in some inorganic semiconductors offers a promising solution, but the deformation mechanisms remain controversial. Here, we investigate the deformation of indium selenide, a two-dimensional van der Waals semiconductor with substantial plasticity. By developing a machine-learned deep potential, we perform atomistic simulations that capture the deformation features of hexagonal indium selenide upon out-of-plane compression. Unexpectedly, we find that indium selenide plastifies through a martensitic transformation; that is, the layered hexagonal structure is converted to a tetragonal lattice with specific orientation relationship. This observation is corroborated by high-resolution experimental observations and theory. It suggests a change of paradigm, where the design of new plastically deformable inorganic semiconductors can focus on compositions and structures that facilitate phase transformations, going beyond the conventional dislocation slip.

Phonons contribute an appreciable proportion of the thermal conductivity of iron-based structural materials used in the nuclear industry. The decrease in thermal conductivity caused by defects such as dislocations will decrease the efficiency of nuclear reactors or lead to melting failure under transient heat flow. However, the phonon–dislocation scattering rate in iron is unknown, and the details of the scattering process have not been well studied. In this paper, the effect of dislocations on lattice thermal conductivity in pure iron is studied using molecular dynamics simulations. The temperature distribution in the neighborhood of the dislocation, the spectral heat flux, and the frequency-dependent phonon mean free paths are obtained. From a comparison with the results for a perfect crystal, we find that the dislocation can significantly decrease the lattice thermal conductivity. By using an average phonon group velocity, the phonon–dislocation scattering rate under a given dislocation density is obtained from the phonon mean free paths. Moreover, eigenmode analysis of a dislocation dipole model indicates that the phonons have a certain degree of localization, which reduces their ability to transport heat. Our study reveals the details of the phonon–dislocation scattering process and may help to interpret the reduced thermal conductivity caused by the dislocations that are generated during the service lives of iron-based structural materials.

The spatially resolved phonon dislocation scattering process: phonons are scattered or slowed down by the local strain region and dislocation core.

Thermal management is extremely important for designing high-performance devices. The lattice thermal conductivity of materials is strongly dependent on detailed structural defects at different length scales, particularly point defects like vacancies, line defects like dislocations, and planar defects such as grain boundaries. Traditionally, the McKelvey–Shockley phonon Boltzmann’s transport equation (BTE) method, combined with molecular dynamics simulations, has been widely used to evaluate the phonon mean free paths (MFPs) in defective systems. However, this method can only provide the aggregate MFPs of the whole sample, as it is challenging to extract the MFPs in different regions with varying thermal conductivities. In this study, the 1D McKelvey–Shockley phonon BTE method was extended to model inhomogeneous materials, where the contributions of defects to the phonon MFPs are explicitly obtained. Then, the method was used to study the phonon scattering with the core structure of an edge dislocation. The phonon MFPs in the dislocation core were obtained and were found to be consistent with the analytical model in a way that high frequency phonons are likely to be scattered in this area. This method not only advances the knowledge of phonon–dislocation scattering but also shows the potential to investigate phonon transport behaviors in more complicated materials.