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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Hydration of Atmospheric Molecular Clusters III: Procedure for Efficient Free Energy Surface Exploration of Large Hydrated Clusters
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Hydration of Atmospheric Molecular Clusters III: Procedure for Efficient Free Energy Surface Exploration of Large Hydrated Clusters

机译：大气分子簇III的水合：用于大型水合簇的有效自由能表面探索的程序

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Sampling the shallow free energy surface of hydrated atmospheric molecular clusters is a significant challenge. Using computational methods, we present an efficient approach to obtain minimum free energy structures for large hydrated clusters of atmospheric relevance. We study clusters consisting of two to four sulfuric acid (sa) molecules and hydrate them with up to five water (w) molecules. The structures of the "dry" clusters are obtained using the ABCluster program to yield a large pool of low-lying conformer minima with respect to free energy. The conformers (up to ten) lowest in free energy are then hydrated using our recently developed systematic hydrate sampling technique. Using this approach, we identify a total of 1145 unique (sa)(2-4)(w)(1-5) cluster structures. The cluster geometries and thermochemical parameters are calculated at the omega B97X-D/6-31++G(d,p) level of theory, at 298.15 K and 1 atm. The single-point energy of the most stable clusters is calculated using a high-level DLPNO-CCSD(T-0)/aug-cc-pVTZ method. Using the thermochemical data, we calculate the equilibrium hydrate distribution of the clusters under atmospheric conditions and find that the larger (sa)(3) and (sa)(4) clusters are significantly more hydrated than the smaller (sa)(2) cluster or the sulfuric acid (sa)(1) molecule. These findings indicate that more than five water molecules might be required to fully saturate the sulfuric acid clusters with water under atmospheric conditions. The presented methodology gives modelers a tool to take the effect of water explicitly into account in atmospheric particle formation models based on quantum chemistry.
机译：采样水合大气分子簇的浅无能表面是一个重大挑战。使用计算方法，我们提出了一种有效的方法来获得大型水合簇的最小自由能结构。我们研究由两到四个硫酸（SA）分子组成的簇，并用最多五个水（W）分子水合物。使用缩放程序获得“干燥”簇的结构，以产生相对于自由能量的大量低位符合子最小值。然后使用我们最近开发的系统水合物采样技术来水合在自由能中最低的空转能器（最多十个）。使用此方法，我们确定总共1145个唯一（SA）（2-4）（2-4）（1-5）群集结构。在欧米茄B97X-D / 6-31 ++ G（D，P）理论水平下计算簇几何和热化学参数，在298.15 k和1atm。使用高级DLPNO-CCSD（T-0）/ AUG-CC-PVTZ方法计算最稳定的簇的单点能量。使用热化学数据，我们在大气条件下计算簇的平衡水合物分布，发现较大（SA）和（SA）（SA）（SA）（4）簇明显多于较小的（SA）（2）簇或硫酸（SA）（1）分子。这些发现表明，可能需要多于五种水分子以在大气条件下将硫酸簇充分饱和。所提出的方法为建模者提供了一种工具，该工具在基于量子化学的大气粒子形成模型中明确地考虑水的工具。

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