Accuracy of classical force fields for polyethylene structures away from equilibrium

This study compares the performance of four classical force fields (FFs)—OPLS, PCFF, TraPPE-UA, and ReaxFF—with density functional theory (DFT) for modeling polyethylene (PE) configurations under extreme conditions. We evaluate their accuracy in predicting energies, forces, and stresses. Additionally, the FFs are used to generate a pressure–temperature phase diagram to compare PE’s melting behavior against experimental observations. The results indicate that PCFF and OPLS exhibit the closest agreement with DFT, while PCFF, TraPPE-UA, and ReaxFF perform equally when compared to experimental data. This research provides valuable insights for complex simulations, such as high-pressure shock compression studies on PE.