The Effect of Interstitial Layers on Thermal Boundary Conductance between Lennard-jones Crystals

Thermal transport at the interface between Lennard-Jones crystals is explored via non-equilibrium molecular dynamics simulations. The vibrational properties of each crystal are varied by changing the atomic mass of the crystal. By applying a constant thermal flux across the two-crystal composite system, a steady-state temperature gradient is established and thermal boundary conductance at the interface between the crystals is calculated via Fourier’s law. With the material properties of the two crystals fixed, thermal boundary conductance can be affected by an intermediate layer inserted between the two crystals. It is found that when the interstitial layer atomic mass is between those values of the crystals comprising the interface, interfacial transport is enhanced. This layer helps bridge the gap between the different vibrational spectra of the two materials, thus enhancing thermal transport, which is maximized when the interstitial layer atomic mass approaches the average mass of the two fixed crystals. The degree of enhancement depends on the vibrational mismatch between the interstitial layer and the crystals comprising the interface, and we report an increase in thermal boundary conductance of up to 50 %. NOMENCLATURE F force acting on an atom, [N] hBD thermal boundary conductance, [W m−2 K−1] hBD reduced thermal boundary conductance k thermal conductivity, [W m−1 K−1] kB Boltzmann’s Constant, [J K−1] m atomic mass, [kg] q applied heat flux across the interface, [W m−2] RBD thermal boundary resistance, [m2 K W−1] t time, [s] T temperature, [K] T ∗ reduced temperature U potential energy, [J] v atomic velocity, [m s−1] ε Lennard-Jones parameter, [J] σ Lennard-Jones parameter, [m] ξ scaling factor implemented in NEMD ω vibrational frequency, [Hz] NP number of atoms in a particular slice P