Dr. John C. Duda’s paper published in Journal of Applied Physics – “Bidirectionally tuning Kaptiza conductance through the inclusion of substitutional impurities”

Our paper – Duda et al., “Bidirectionally tuning Kaptiza conductance through the inclusion of substitutional impurities” – was recently published in Journal of Applied Physics (J. Appl. Phys. 112, 073519 (2012)). In this work, we explored methods of tuning the thermal boundary conductance between two solids with molecular dynamics simulations.  We found that the presence of impurities at solid interfaces can lead to an increase in thermal boundary conductance if the masses of the impurities are in between the masses of the atoms on either side of the interface.  This counter-intuitive finding contradicts typical impurity scattering theory in a homogeneous material where impurity scattering will always lead to a decrease in thermal transport, the magnitude of which is governed by the difference in masses.  The increase in Kaptiza conductance due to interfacial impurities is due to a bridging in vibrational states on either side of the interface due to the impurity masses.

Abstract

We investigate the influence of substitutional impurities on Kapitza conductance at coherent interfaces via non-equilibrium molecular dynamics simulations. The reference interface is comprised of two mass-mismatched Lennard-Jones solids with atomic masses of 40 and 120 amu. Substitutional impurity atoms with varying characteristics, e.g., mass or bond, are arranged about the interface in Gaussian distributions. When the masses of impurities fall outside the atomic masses of the reference materials, substitutional impurities impede interfacial thermal transport; on the other hand, when the impurity masses fall within this range, impurities enhance transport. Local phonon density of states calculations indicate that this observed enhancement can be attributed to a spatial grading of vibrational properties near the interface. Finally, for the range of parameters investigated, we find that the mass of the impurity atoms plays a dominant role as compared to the impurity bond characteristics.

This work was funded by NSF (CBET Award #1134311) and Sandia National Laboratories through the LDRD Program Office.