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

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 $\kappa^{\rm exp}$.