Revised atomic charges for OPLS force field model of poly(ethylene oxide): Benchmarks and applications in polymer electrolyte

Poly(ethylene oxide) (PEO)-based polymers are common hosts in solid polymer electrolytes (SPEs) for high-power energy devices. Molecular simulations have provided valuable molecular insights into structures and ion transport mechanisms of PEO-based SPEs. The calculation of thermodynamic and kinetic properties rely crucially on the dependability of the molecular force fields describing inter- and intra-molecular interactions with the target system. In this work, we reparametrized atomic partial charges for the widely applied optimized potentials for liquid simulations (OPLS) force field of PEO. The revised OPLS force field, OPLS^R, improves the calculations of density, thermal expansion coefficient, and the phase transition of the PEO system. In particular, OPLS^R greatly enhances the accuracy of the calculated dielectric constant of PEO, which is critical for simulating polymer electrolytes. The reparameterization method was further applied to SPE system of PEO/LiTFSI with O:Li ratio of 16:1. Based on the reparametrized partial charges, we applied separate charge-scaling factors for PEO and Li salts. The charge-rescaled OPLS^R model significantly improves the resulting kinetics of Li⁺ transport while maintaining the accurate description of coordination structures within PEO-based SPE. The proposed OPLS^R force field can benefit the future simulation studies of SPE systems.