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 the measurements of $\kappa$ in comparison to those of the experiments 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 nontrivial. In this work, two semianalytical approaches are considered to accurately compute $\kappa$ by using the exact vibrational density of states $g\left(\nu \right)$. The first approach is based within the framework of the minimum thermal conductivity model, while the second uses computed quantum heat capacity to scale $\kappa$. The computed $\kappa$ of a set of commodity polymers compares quantitatively with ${\kappa }^{\mathrm{expt}}$.