  Polymer simulations routinely employ models with different molecular
resolutions. United atom (UA) models are one such example, where groups of
certain atoms in a molecule are clustered into superatoms. Although their
computational simplicity makes them particularly attractive for studying a wide
range of polymer properties, the missing degrees of freedom in UA models can
impact certain properties that are intimately linked to localized vibrations,
such as the heat capacity and the thermal transport coefficient $\kappa$. In
contrast, the numerically exhausting all atom (AA) models produce results that
better match experimental data. In this work, we systematically investigate and
compare $\kappa$ obtained from an AA and a UA models for an amorphous
polyethylene system. The results indicate that the UA description may not be a
suitable model for evaluating thermal transport, since it underestimates
$\kappa$ in comparison to an AA description and the experimental value. The
coarse-graining leads to the softer interactions and its presence is
highlighted in a weaker mechanical response from the UA model, thus also
underestimates $\kappa$. We further consolidate our findings by extracting the
bonded and the nonbonded contributions to $\kappa$ within the framework of the
single chain energy transfer model.
