Polarizable Split-Charge Equilibration for Accurate Modeling of Nonbonded Interactions.

Accurate modeling of nonbonded interactions remains challenging because conventional force fields often provide inadequate descriptions of polarization and charge transfer. Here, we introduce a polarizable split-charge equilibration (PSQ) framework that combines localized charge flow with dipolar polarization, thereby mitigating the unphysical long-range charge delocalization associated with polarizable charge-equilibration models. To enable practical large-scale simulations, we develop an efficient PSQ implementation through algorithmic optimization and parallelization, achieving performance comparable to conventional approaches despite the model's greater formal complexity. We combine PSQ with the universal nonbond potential for van der Waals interactions and an explicit four-body hydrogen-bond term to form the PUxH framework. PUxH achieves near-chemical accuracy in predicting small-molecular pair interactions and accurately reproduces the bulk properties of water, ammonia, and benzene. Overall, PUxH provides a transferable, physically grounded, and computationally efficient framework for modeling nonbonded interactions in molecular and condensed-phase systems.