(86f) Explicit Solvent Hybrid QM Simulations Embedded in the Quantum-Based Polarizable Reactive Force Field

Multiscale reactive simulations of materials and energy systems at the accuracy level of ab-initio methods are required to make significant breakthroughs in the design and discovery of novel complex materials. Hybrid quantum mechanics/molecular mechanics (QM/MM) methods have often been used to enable QM accuracy for the key reactive part of a system while using a force field for the dynamics of more distant atoms. Generally the electrostatics and polarizations across the boundary of the QM and MM subsystems is poorly described, limiting the accuracy. Recently, we developed a new generic reactive force field, RexPoN, capable of describing complex reaction dynamics including polarization at nearly the accuracy of QM for systems with 10,000 to 1 million atoms, which we have validated with several applications. Here, we introduce a new hybrid QM/MM framework, RexPoN embedded QM, or ReQM, for practical multi-scale simulations of systems containing millions of atoms, but for which the long range interactions in the polarizable Reactive field (PRD) match accurately those of QM. ReQM is suitable for applications such reactive simulations as electrocatalysis, that require accurate full explicit description of the solvent . We validate the accuracy of ReQM by computing the vibrational density of states of reaction intermediates during CO₂ reduction reactions and comparing against operando electrocatalysis and full solvent QM calculations.