Abstract
Heat transport can be modelled with a variety of approaches in real space (using molecular dynamics) or in reciprocal space (using the Boltzmann transport equation). Employing two conceptually different approaches of each type, we study heat transport in crystalline polyethylene and polythiophene. We find that consistent results can be obtained when using highly efficient and accurate machine-learned potentials, provided that the physical intricacies of the considered materials and methods are correctly accounted for. For polythiophene, this turns out to be comparably straightforward, whereas for polyethylene, we find that the inclusion of higher-order anharmonicities is crucial to avoid a massive overestimation of the thermal conductivity. The responsible long-lived phonons are found at relatively high frequencies between 11 THz and 16 THz. This complicates the use of classical statistics in all molecular-dynamics-based approaches.
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Data availability
Datasets generated and/or analysed during the current study are available in the TU Graz Repository; https://doi.org/10.3217/jw2ym-g7r83.
Code availability
The modified version of Dynaphopy, that was used in this study, is available at www.github.com/sandrowieser/DynaPhoPy/tree/orig-ez-paper. VASP can be acquired from the VASP Software GmbH (see www.vasp.at); LAMMPS is available at www.lammps.org; MLIP is available at www.mlip.skol-tech.ru/download; the lammps-mlip interface (version 2) is available at www.gitlab.com/ashapeev/interface-lammps-mlip-2; Phonopy is available at www.phonopy.github.io/phonopy; Phono3py is available at www.phonopy.github.io/phono3py.
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Acknowledgements
This research was funded in whole, or in part, by the Austrian Science Fund (FWF) [primarily Grant-https://doi.org/10.55776/P33903 and in part also https://doi.org/10.55776/P36129]. For the purpose of open access, the authors have applied a CC-BY public copyright license to any author accepted manuscript version arising from this submission. We also acknowledge the Graz University of Technology for support through the Lead Project Porous Materials @ Work for Sustainability (LP-03). The computational results have been achieved using the Austrian Scientific Computing (ASC) infrastructure, clusters VSC-4 and VSC-5.
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Conceptualization, E.Z. and L.R.; methodology, L.R. and S.W.; software, L.R. and S.W.; validation, L.R.; formal analysis, L.R.; investigation, L.R.; resources, E.Z.; data curation, L.R.; writing-original draft preparation, L.R.; writing-review and editing, E.Z., L.R., L.L., and S.W.; visualization, L.R.; supervision, E.Z.; project administration, E.Z.; funding acquisition, E.Z. All authors have read and agreed to the published version of the manuscript.
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Reicht, L., Legenstein, L., Wieser, S. et al. Analysing heat transport in crystalline polymers in real and reciprocal space. npj Comput Mater (2026). https://doi.org/10.1038/s41524-026-01988-0
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DOI: https://doi.org/10.1038/s41524-026-01988-0
