Computing the thermal transport coefficient of neutral amorphous polymers using exact vibrational density of states: Comparison with experiments

TL;DR

This paper introduces two semi-analytical methods leveraging the exact vibrational density of states to accurately compute the thermal transport coefficient of amorphous polymers, aligning well with experimental data.

Contribution

It presents novel approaches that incorporate quantum effects via vibrational density of states to improve thermal conductivity predictions in polymers.

Findings

Computed thermal conductivities match experimental values.

Quantum effects significantly influence thermal transport calculations.

The methods outperform classical simulation overestimations.

Abstract

Thermal transport coefficient $\kappa$ is an important property that often dictates broad applications of a polymeric material, while at the same time its computation remains challenging. In particular, classical simulations overestimate $\kappa$ than the experimentally measured $\kappa^{\rm exp}$ and thus hinder their meaningful comparison. This is even when very careful simulations are performed using the most accurate empirical potentials. A key reason for such a discrepancy is because polymers have quantum--mechanical, nuclear degrees--of--freedom whose contribution to the heat balance is non--trivial. In this work, two semi--analytical approaches are considered to accurately compute $\kappa$ by using the exact vibrational density of states $g(\nu)$. The first approach is based within the framework of the minimum thermal conductivity model, while the second uses computed quantum heat capacity to scale $\kappa$. Computed $\kappa$ of a set of commodity polymers compares quantitatively with $\kappa^{\rm exp}$.