Investigation of Thermal Transport Properties in van der Waal Layered Materials With Threading Screw Dislocations

Threading screw dislocations in van der Waals (vdW) layered materials result in large strain and disordered atomic registry that can lead to profound changes in thermal transport properties of materials. In this study, we investigate thermal conductivities in graphite with threading screw dislocations along the vdW-bonded direction. In the first part of the study, we provide an atomistic level understanding of a newly discovered threading dislocation core structure. From sequential structure relaxations with an analytical bond-order potential and an adaptive intermolecular reactive empirical bond order (AIREBO) potential, we identify an energetically favorable sp³-bonded core, which imposes a tensile strain along the vdW-bonded direction. An analytical elastic spring core – shell model is used to estimate the elastic stiffness and the equilibrium length of the dislocation core. In the second part of the study, we compute thermal conductivities of graphite with and without dislocations using equilibrium molecular dynamics with the Green-Kubo method and the AIREBO potential. The heat-current autocorrelation curve is fitted to a double exponential function corresponding to a two-stage decay process. Furthermore, we apply strain along the vdW-bonded direction and observe a clear difference in thermal conductivities in structures with and without dislocations. We then discuss factors that changes thermal conductivities: the sp³ bonds in the dislocation core, the tensile strain in the dislocation core, and the scattering of phonons due to dislocations. This study provides a fundamental understanding of the role of threading screw dislocations in nanoscale thermal transport in vdW layered materials and contributes to the development of advanced thermal applications. The authors acknowledge the support of the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under contract no. DE-AC02-05Ch11231 (Electronic Materials Program).