Influence of crystallographic orientation and anisotropy on Kapitza conductance via classical molecular dynamics simulations

Abstract

We investigate the influence of crystallographic orientation and anisotropy on local phonon density of states, phonon transmissivity, and Kapitza conductance at interfaces between Lennard-Jones solids via classical molecular dynamics simulations. In agreement with prior works, we find that the Kapitza conductance at an interface between two face-centered cubic materials is independent of crystallographic orientation. On the other hand, at an interface between a face-centered cubic material and a tetragonal material, the Kapitza conductance is strongly dependent on the relative orientation of the tetragonal material, albeit this dependence is subject to the overlap in vibrational spectra of the cubic and tetragonal materials. Furthermore, we show that interactions between acoustic phonons in the cubic material and optical phonons in the tetragonal material can lead to the interface exhibiting greater “thermal anisotropy” as compared to that of the constituent materials. Finally, it is noted that the relative match or mismatch between the Debye temperatures of two materials comprising an interface does not serve an accurate gauge of the efficiency of interfacial thermal transport when those materials have different crystal structures.

Relationship of thermal boundary conductance to structure from an analytical model plus molecular dynamics simulations

“…In order to further generalize our results, we have studied the effect of rectangular morphologies at a massmismatched A/B Lennard-Jones (LJ) type interfaces using a similar approach described previously 32,60 . The computational cells contain 8 × 8 × 80 conventional unit cells (5.25Å/cell) of an fcc crystal with 20,480 atoms.…”

Investigation of size and electronic effects on Kapitza conductance with non-equilibrium molecular dynamics

“…Once the systems were relaxed and thermalized, equal and opposite heat fluxes were applied to "hot" and "cold" regions as in the usual application of the "direct" method of measuring thermal conductivity. 28,35,36 The energy flux was effected by controlling the input of kinetic energy over time. [37][38][39][40] This flux-control scheme, together with Verlet dynamics, maintained a constant system energy throughout the data collection phase.…”

Bidirectionally tuning Kapitza conductance through the inclusion of substitutional impurities

“…However, other qualities of the interface can influence Kapitza conductance, including interfacial structure, [12][13][14][15][16][17][18][19][20][21][22] interfacial chemistry, [23][24][25][26][27][28][29][30] and the relative orientation of the constituent materials. 12,[31][32][33][34][35] With regard to interface structure, deviations from "ideality" can include one or a combination of several unique features, e.g., compositional mixing, 9,22 dislocations, 16 confined films, 21,22 non-crystallinity, 13 or nanometer-scale geometric facets. 15,[18][19][20] When compared to ideal interfaces, certain combinations of these features have been found to enhance Kapitza conductance, 9,21,22 while others have been shown to reduce it.…”