Lu Jibao, Qiu Yuqing, Baron Riccardo, Molinero Valeria
Department of Chemistry, The University of Utah , Salt Lake City, Utah 84112-0850, United States.
Department of Medicinal Chemistry, The University of Utah , Salt Lake City, Utah 84112-5820, United States.
J Chem Theory Comput. 2014 Sep 9;10(9):4104-20. doi: 10.1021/ct500487h. Epub 2014 Aug 1.
Coarse-grained models are becoming a competitive alternative for modeling processes that occur over time and length scales beyond the reach of fully atomistic molecular simulations. Ideally, coarse-grained models should not only achieve high computational efficiency but also provide accurate predictions and fundamental insight into the role of molecular interactions, the characteristic behavior, and properties of the system they model. In this work we derive a series of monatomic coarse-grained water models mX(REM) from the most popular atomistic water models X = TIP3P, SPC/E, TIP4P-Ew, and TIP4P/2005, using the relative entropy minimization (REM) method. Each coarse-grained water molecule is represented by a single particle that interacts through short-ranged anisotropic interactions that encourage the formation of "hydrogen-bonded" structures. We systematically investigate the features of the coarse-grained models in reproducing over 20 structural, dynamic, and thermodynamic properties of the reference atomistic water models-including the existence and locus of the characteristic density anomaly. The mX(REM) coarse-grained models reproduce quite faithfully the radial and angular distribution function of water, produce a temperature of maximum density (TMD), and stabilize the ice I crystal. Moreover, the ratio between the TMD and the melting temperature of the crystal in the mX(REM) models and liquid-ice equilibrium properties show reasonable agreement with the results of the corresponding atomistic models. The mX(REM) models, however, severely underestimate the cohesive energy of the condensed water phases. We investigate which specific limitations of the coarse-grained models arise from the REM methodology, from the monatomic nature of the models, and from the Stillinger-Weber interaction potential form. Our analysis indicates that a small compromise in the accuracy of structural properties can result in a significant increase of the overall accuracy and representability of the coarse-grained water models. We evaluate the accuracy of the atomistic and the monatomic anisotropic coarse-grained water models, including the mW water model, in reproducing experimental water properties. We find that mW and mTIP4P/2005(REM) score closer to experiment than widely used atomistic water models. We conclude that monatomic models of water with short-range, anisotropic "hydrogen-bonding" three-body interactions can be competitive in accuracy with fully atomistic models for the study of a wide range of properties and phenomena at less than 1/100th of the computational cost.
粗粒度模型正成为一种具有竞争力的替代方法，用于对发生在时间和长度尺度上超出全原子分子模拟范围的过程进行建模。理想情况下，粗粒度模型不仅应实现高计算效率，还应提供准确的预测，并深入了解分子相互作用的作用、它们所建模系统的特征行为和性质。在这项工作中，我们使用相对熵最小化（REM）方法，从最流行的全原子水模型X = TIP3P、SPC/E、TIP4P-Ew和TIP4P/2005中推导出一系列单原子粗粒度水模型mX(REM)。每个粗粒度水分子由单个粒子表示，该粒子通过短程各向异性相互作用相互作用，这种相互作用促进了“氢键”结构的形成。我们系统地研究了粗粒度模型在重现参考全原子水模型的20多种结构、动力学和热力学性质方面的特征，包括特征密度异常的存在和位置。mX(REM)粗粒度模型相当忠实地重现了水的径向和角分布函数，产生了最大密度温度（TMD），并稳定了冰I晶体。此外，mX(REM)模型中TMD与晶体熔化温度之间的比率以及液-冰平衡性质与相应全原子模型的结果显示出合理的一致性。然而，mX(REM)模型严重低估了凝聚水相的内聚能。我们研究了粗粒度模型的哪些具体局限性源于REM方法、模型的单原子性质以及Stillinger-Weber相互作用势形式。我们的分析表明，在结构性质的准确性上做出小的妥协可以导致粗粒度水模型的整体准确性和可表示性显著提高。我们评估了全原子和单原子各向异性粗粒度水模型（包括mW水模型）在重现实验水性质方面的准确性。我们发现，mW和mTIP4P/2005(REM)在得分上比广泛使用的全原子水模型更接近实验结果。我们得出结论，具有短程、各向异性“氢键”三体相互作用的单原子水模型在准确性上可以与全原子模型相竞争，用于研究广泛的性质和现象，而计算成本不到全原子模型的1/100。
