Spatially Local Estimates of the Thermal Conductivity of Materials

TL;DR

This paper introduces a spatial decomposition method for thermal conductivity, called site-projected thermal conductivity, to analyze local heat transport properties in amorphous and crystalline materials using the Green-Kubo formula.

Contribution

It presents a novel approach to quantify local thermal conduction activity at each site, linking structural features to heat transport in complex materials.

Findings

Identifies structural sites that reduce heat transport.

Quantifies the spatial range of thermal defects.

Reveals similarities between heat transport and electronic structure features.

Abstract

In this paper we describe a spatial decomposition of the thermal conductivity, what we name "site-projected thermal conductivity", a gauge of the thermal conduction activity at each site. The method is based on the Green-Kubo formula and the harmonic approximation, and requires the force-constant and dynamical matrices and of course the structure of a model sitting at an energy minimum. Throughout the paper, we use high quality models previously tested and compared to many experiments. We discuss the method and underlying approximations for amorphous silicon, carry our detailed analysis for amorphous silicon, then examine an amorphous-crystal silicon interface, and representative carbon materials. We identify the sites and local structures that reduce heat transport, and quantify these (estimate the spatial range) over which these "thermal defects" are effective. Similarities emerge between these filamentary structures in the amorphous silicon network which impact heat transport, electronic structure (the Urbach edge) and electronic transport.