Comparing simulated specific heat of liquid polymers and oligomers to experiments

The field of atomistic simulations of polymers is in a mature stage, yet accurate predictions of their specific heat are very rare. The main difficulty stems from the quantum-mechanical nature of intramolecular vibrations. They call for either full, tedious quantum-mechanical treatments, or, for proper corrections of classical simulations. Here, the authors adopt an existing method, 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, they predominantly correct the stiff, high-frequency harmonic modes, while leaving the specific-heat contributions of the slow (anharmonic) modes intact. The results compare well to experimental data.