Tuning the Through-Plane Lattice Thermal Conductivity in van der Waals Structures through Rotational (Dis)ordering

Abstract

It has recently been demonstrated that MoS 2 with irregular interlayer rotations can achieve an extreme anisotropy in the lattice thermal conductivity (LTC), which is, for example, of interest for applications in waste heat management in integrated circuits. Here, we show by atomic-scale simulations based on machine-learned potentials that this principle extends to other two-dimensional materials, including C and BN. In all three materials, introducing rotational disorder drives the through-plane LTC to the glass limit, while the in-plane LTC remains almost unchanged compared to those of the ideal bulk materials. We demonstrate that the ultralow through-plane LTC is connected to the collapse of their transverse acoustic modes in the through-plane direction. Furthermore, we find that the twist angle in periodic moiré structures representing rotational order provides an efficient means for tuning the through-plane LTC that operates for all chemistries considered here. The minimal through-plane LTC is obtained for angles between 1 and 4° depending on the material, with the biggest effect in MoS 2 . The angular dependence is correlated with the degree of stacking disorder in the materials, which in turn is connected to the slip surface. This provides a simple descriptor for predicting the optimal conditions at which the LTC is expected to become minimal.

Combining the D3 dispersion correction with the neuroevolution machine-learned potential

“…Therefore, it has been suggested to use a relatively longer cutoff for the radial descriptor components r R c in combination with a relatively shorter cutoff for the angular descriptor components r A c when this is beneficial [16]. For example, this strategy has been used for modeling a number of vdW structures [20,21] that have both strong covalent bonds and weak vdW interactions, where r R c was taken to be about 7-8 Å and r A c 3-4 Å. While constructing a pure NEP that incorporates dispersion interactions is feasible, the primary objective of this work is to introduce the NEP-D3 method that addresses dispersion interactions in a more elegant manner.…”