Efficient Anharmonic Lattice Dynamics Calculations of Thermal Transport in Crystalline and Disordered Solids

TL;DR

This paper introduces a unified, scalable computational workflow combining BTE and QHGK methods for anharmonic lattice dynamics, enabling accurate thermal transport simulations in both crystalline and disordered solids like silicon and silicon-germanium alloys.

Contribution

It presents a novel unified approach and software implementation for simulating heat transport in both crystalline and amorphous materials using anharmonic lattice dynamics.

Findings

Effective simulation of thermal conductivity in silicon and alloys.

Reduced thermal conductivity in silicon-germanium alloy clathrates.

Scalable implementation optimized for modern parallel architectures.

Abstract

Understanding heat transport in semiconductors and insulators is of fundamental importance because of its technological impact in electronics and renewable energy harvesting and conversion. Anharmonic Lattice Dynamics provides a powerful framework for the description of heat transport at the nanoscale. One of the advantages of this method is that it naturally includes quantum effects due to atoms vibrations, which are needed to compute the thermal properties of semiconductors widely used in nanotechnology, like silicon and carbon, even at room temperature. While the heat transport picture substantially differs between amorphous and crystalline semiconductors from a microscopic standpoint, a unified approach to simulate both crystals and glasses has been devised. Here we introduce a unified workflow, which implements both the Boltzmann Transport equation (BTE) and the Quasi Harmonic Green-Kubo (QHGK) methods. We discuss how the theory can be optimized to exploit modern parallel architectures, and how it is implemented in $\kappa ALDo$: a versatile and scalable open-source software to compute phonon transport in solids. This approach is applied to crystalline and partially disordered silicon-based systems, including bulk silicon and clathrates, and on silicon-germanium alloy clathrates with largely reduced thermal conductivity.