SKM 2021 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 15: Theory and Simulation (joint session CPP/DY)
CPP 15.5: Talk
Friday, October 1, 2021, 14:45–15:00, H3
How to accurately estimate the specific heat of liquid polymers? — •Debashish Mukherji1, Hongyu Gao2, Tobias P. W. Menzel2, and Martin H. Mueser2 — 1Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada — 2Department of Materials Science and Engineering, Saarland University, 66123 Saarbruecken, Germany
The field of atomistic simulations of polymers is in a mature stage, yet predictions of specific heat from molecular simulations and successful comparisons with experimental data are scarce if existing at all. One reason for this may be that the internal energy and thus the specific heat cannot be coarse-grained so that they defy their rigorous computation with united-atom models. Moreover, many modes in a polymer barely contribute to the specific heat because of their quantum mechanical nature. Here, we adopt an existing method [1], which defines a specific heat for a harmonic reference, to estimate the specific heat difference between classical and quantum-mechanical systems and use this as a correction factor. Thereby, we predominantly correct the stiff, high-frequency harmonic modes, while leaving the specific-heat contributions of the slow (anharmonic) modes intact [2]. We show how to construct corrections for both all-atom and united-atom descriptions of chain molecules. Corrections computed for a set of hydrocarbon oligomers and commodity polymers deviate by less than kB/10 per particle. The results compare well with experimental data.
[1] Horbach, Kob, and Binder, JPCB 103, 4104 (1999). [2] Gao, Menzel, Mueser, and Mukherji, PRM 5, 065605 (2021).