Tunable Anisotropic Lattice Thermal Conductivity in One-Dimensional Superlattices from Molecular Dynamics Simulations

摘要

Engineering nanostructured superlattices provides an effective solution toward the realization of high-performance thermoelectric device and thermal management materials,where the anisotropic thermal conductivity is critical for designing orientation-dependent thermal devices.Herein,the lattice thermal conductivity anisotropy of Al/Ag superlattices as one typical example of superlattice materials is investigated utilizing non-equilibrium molecular dynamics simulations.The cross-plane and in-plane lattice thermal conductivities of one-dimensional superlattices are in the ranges of 0.5–3.2 W/(m·K)and 1.8–5.1 W/(m·K)at different period lengths,respectively,both of which are smaller than those of bulk materials.More specifically,the cross-plane lattice thermal conductivity of superlattices increases with the period length,while the in-plane phonon thermal conductivity first increases and then trends to convergence,resulting in the non-monotonic thermal anisotropy value.To further reveal the microscopic phonon transport mechanism,the interfacial phonon thermal resistance,density of states and spectral phonon transmission coefficient including anharmonic phonon properties under different period lengths are calculated.Our results can be helpful for understanding phonon transport in low-dimensional materials and provide guidance for optimizing the thermal conductivity anisotropy of superlattice materials in the application ranging from thermoelectric devices to thermal management in micro/nano systems.