High-Throughput Calculations of Thermal Conductivity in Nanoporous Materials: The Case of Half-Heusler Compounds

TL;DR

This paper presents a high-throughput computational approach to predict thermal conductivity in nanoporous half-Heusler compounds, emphasizing the importance of combined bulk properties and nanostructure geometry for thermal management.

Contribution

It introduces a novel phonon mean-free-path dependent Boltzmann transport model that enables rapid screening of materials for low thermal conductivity in nanostructured systems.

Findings

Thermal conductivity depends on bulk phonon MFP distribution and nanostructure size.

The ordering of nanostructure thermal conductivities can differ from bulk.

A fast model for high-throughput screening of thermally optimized materials.

Abstract

Achieving low thermal conductivity and good electrical properties is a crucial condition for thermal energy harvesting materials. Nanostructuring offers a very powerful tool to address both requirements: in nanostructured materials, boundaries preferentially scatter phonons compared to electrons. The search for low-thermal-conductivity nanostructures is typically limited to materials with simple crystal structures, such as silicon, because of the complexity arising from modeling branch- and wave vector- dependent nanoscale heat transport. Using the phonon mean-free-path (MFP) dependent Boltzmann transport equation, a model that overcomes this limitation, we compute thermal transport in 75 nanoporous half-Heusler compounds for different pore sizes. We demonstrate that the optimization of thermal transport in nanostructures should take into account both bulk thermal properties and geometry-dependent phonon suppression, two aspects that are typically engineered separately. In fact, our work predicts that, given a set of bulk materials and a system geometry, the ordering of the thermal conductivity of the nanostructure does not necessarily align with that of the bulk: We show that what dictates thermal transport is the interplay between the bulk MFP distribution and the nanostructuring length scale of the material. Finally, we derive a thermal transport model that enables fast systems screening within large bulk material repositories and a given geometry. Our study motivates the need for a holistic approach to engineering thermal transport and provides a method for high-throughput materials discovery.