Development and Implementation of Atomically Anisotropic First-Principles Force Fields: A Benzene Case Study

π-interactions are an important
motif in chemical and biochemical
systems. However, due to their anisotropic electron densities and
complex balance of intermolecular interactions, aromatic molecules
represent an ongoing challenge for accurate and transferable force
field development. Historically, ab initio force
fields for aromatics have not exhibited good accuracy with respect
to bulk properties or have only been used to study gas-phase dimers.
Using benzene as a proof of concept, herein we show how our own ab initio MASTIFF force field incorporates an atomically
anisotropic description of intermolecular interactions to yield an
accurate and robust model for aromatic interactions irrespective of
phase. Compared to existing models, the MASTIFF benzene force field
not only is accurate for liquid phase properties but also offers transferability
to the gas and solid phases. Additionally, we introduce a computationally
efficient OpenMM plugin which enables customizable anisotropic intermolecular
functional forms and which can be generically used in any MD simulation
where a model for nonspherical atomic features is required. Overall,
our results demonstrate the importance of atomic-level anisotropy
in enabling next-generation ab initio force field
development.

π相互作用（π-interactions）是化学与生化体系中一类重要的结构基元。然而，由于其电子密度具有各向异性，且分子间相互作用的平衡关系复杂，芳香族分子的精准且可迁移力场开发始终是一项极具挑战性的课题。过往用于芳香族体系的从头算（ab initio）力场，要么在体相性质预测上精度不足，要么仅能用于气相二聚体的研究。本研究以苯作为概念验证对象，阐明了自研的从头算MASTIFF力场如何通过引入原子级各向异性的分子间相互作用描述方式，构建出精准且鲁棒的芳香相互作用模型，且该模型不受相态限制。与现有模型相比，MASTIFF苯力场不仅在液相性质预测上具备高精度，还可迁移至气相与固相体系中使用。此外，本研究还推出了一款计算高效的OpenMM插件，该插件支持可定制的各向异性分子间相互作用泛函形式，可通用应用于所有需要非球形原子特征模型的分子动力学（MD）模拟场景。综上，本研究结果证实了原子级各向异性对于开发下一代从头算力场的重要意义。