Lambros Eleftherios, Paesani Francesco
Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, USA.
J Chem Phys. 2020 Aug 14;153(6):060901. doi: 10.1063/5.0017590.
We present a systematic analysis of state-of-the-art polarizable and flexible water models from a many-body perspective, with a specific focus on their ability to represent the Born-Oppenheimer potential energy surface of water from the gas to the liquid phase. Using coupled cluster data in the completed basis set limit as a reference, we examine the accuracy of the polarizable models in reproducing individual many-body contributions to interaction energies and harmonic frequencies of water clusters and compare their performance with that of MB-pol, an explicit many-body model that has been shown to correctly predict the properties of water across the entire phase diagram. Based on these comparisons, we use MB-pol as a reference to analyze the ability of the polarizable models to reproduce the energy landscape of liquid water under ambient conditions. We find that, while correctly reproducing the energetics of minimum-energy structures, the polarizable models examined in this study suffer from inadequate representations of many-body effects for distorted configurations. To investigate the role played by geometry-dependent representations of 1-body charge distributions in reproducing coupled cluster data for both interaction and many-body energies, we introduce a simplified version of MB-pol that adopts fixed atomic charges and demonstrate that the new model retains the same accuracy as the original MB-pol model. Based on the analyses presented in this study, we believe that future developments of both polarizable and explicit many-body models should continue in parallel and would benefit from synergistic efforts aimed at integrating the best aspects of the two theoretical/computational frameworks.
我们从多体角度对当前最先进的可极化灵活水模型进行了系统分析，特别关注它们从气相到液相表征水的玻恩 - 奥本海默势能面的能力。以完备基组极限下的耦合簇数据作为参考，我们检验了可极化模型在重现水团簇相互作用能和谐波频率的各个多体贡献方面的准确性，并将它们的性能与MB - pol模型进行比较，MB - pol是一个显式多体模型，已被证明能正确预测整个相图中水的性质。基于这些比较，我们以MB - pol为参考来分析可极化模型在环境条件下重现液态水能量景观的能力。我们发现，虽然所研究的可极化模型能正确重现最低能量结构的能量学，但对于扭曲构型的多体效应表示不足。为了研究单体质荷分布的几何依赖表示在重现相互作用能和多体能量的耦合簇数据中所起的作用，我们引入了一个采用固定原子电荷的MB - pol简化版本，并证明新模型与原始MB - pol模型具有相同的准确性。基于本研究中的分析，我们认为可极化和显式多体模型的未来发展应继续并行，并将受益于旨在整合这两个理论/计算框架最佳方面的协同努力。
