Molecular Dynamics Prediction of the Thermal Resistance of Solid-Solid Interfaces in Superlattices

Abstract

Molecular dynamics simulations are used to predict the thermal resistance of solid-solid interfaces in crystalline superlattices using a new Green-Kubo formula. The materials on both sides of the interfaces studied are modeled with the LennardJones potential and are only differentiated by their masses. To obtain the interface thermal resistance, a correlation length in the bulk materials is first predicted, which approaches a systemsize independent value for larger systems. The interface thermal resistance is found to initially increase as the layer length is increased, and then to decrease as the phonon transport shifts from a regime dominated by ballistic transport to one dominated by diffusive transport. NOMENCLATUREA area E energy F force vector k thermal conductivity k B Boltzmann constant L length m mass r particle position vector, particle separation vector q planar energy flux R thermal resistance R m mass ratio

The role of interface thermal boundary resistance in the overall thermal conductivity of Si–Ge multilayered structures

“…(11) Figure 9 shows a comparison of MD values with the analytical expression (equations ( 10) and ( 11)) predicted values. As shown, we obtain a strong agreement between MD calculated values and the values obtained using equation (11). We also observe a disagreement between values obtained using equation (10) and MD values for higher numbers of periods.…”

“…It has been shown that below a critical period thickness value, the phenomenon of diffuse interface scattering plays a significant role in reducing the thermal conductivity, while above the critical period thickness, dislocations have a significant effect on the superlattice thermal conductivity. A drop in thermal conductivity values is found to occur with decreasing thin film thickness [9][10][11]. Simkin and Mahan [12] theoretically analyzed first the decrease and then the increase in thermal conductivity values of thin film superlattices as a function of decreasing film thickness in order to understand the role of ballistic phonon transport in thermal conduction.…”

Molecular Dynamics Simulations and Thermal Transport at the Nano-Scale

“…Equilibrium simulations have been performed for interface between simple Lennard Jones solids, where the dissimilarity between the two solids is introduced by changing the acoustic impedance ratio between the two solids. The results were found to disagree with NEMD determinations of the Kapitza conductance (McGaughey 2006), especially for solids with a weak acoustic mismatch. These discrepancies are not surprising and can be traced back to the formulation of the equations themselves (Pettersson 1990), as the Green-Kubo formula above predicts a finite conductance for the interface between two identical media, while of course in NEMD one measures an infinite conductance in this situation.…”

Temperature dependence of phonon-defect interactions: phonon scattering vs. phonon trapping

“…No assumption is made about the nature of the thermal transport. In thermal equilibrium 32 33 34 35 36 37 , the system has a constant average temperature and the average heat flux is zero, but a finite heat flux is caused by fluctuations. The decay of the fluctuations of the interfacial energy flux is recorded and interfacial resistance (or conductance) is obtained via the fluctuation-dissipation theorem.…”