大气分子簇的水合作用III：大型水合簇的有效自由能表面探索的程序。,The Journal of Physical Chemistry A

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大气分子簇的水合作用III：大型水合簇的有效自由能表面探索的程序。
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2020-05-28 , DOI: 10.1021/acs.jpca.0c02932
Freja Rydahl Rasmussen ₁ , Jakub Kubečka ₂ , Vitus Besel ₂ , Hanna Vehkamäki ₂ , Kurt V Mikkelsen ₃ , Merete Bilde ₄ , Jonas Elm ₄

Affiliation

对水合大气分子簇的浅自由能表面进行采样是一项重大挑战。使用计算方法，我们提出了一种有效的方法来获取与大气相关的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）分子水合它们。使用ABCluster程序可获取“干”簇的结构，从而产生大量的自由能低层构象极小值池。然后使用我们最近开发的系统水合物采样技术对游离能最低的构象异构体（最多十个）进行水合。使用这种方法，我们确定了总共1145个唯一（sa）_2-4（w）_1-5集群结构。在ωB97X-D/ 6-31 ++ G（d，p）的理论水平上，在298.15 K和1个大气压下计算团簇几何形状和热化学参数。使用高级DLPNO-CCSD（T ₀）/ aug-cc-pVTZ方法计算最稳定簇的单点能量。使用热化学数据，我们计算了大气条件下各簇的平衡水合物分布，发现较大的（sa）₃和（sa）₄簇比较小的（sa）₂簇或硫酸（sa ）₁分子。这些发现表明，在大气条件下，可能需要五个以上的水分子才能使水完全浸透硫酸簇。提出的方法为建模人员提供了一种工具，可以在基于量子化学的大气颗粒形成模型中明确考虑水的影响。

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Hydration of Atmospheric Molecular Clusters III: Procedure for Efficient Free Energy Surface Exploration of Large Hydrated Clusters.

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 ωB97X-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(T₀)/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.

更新日期：2020-06-25

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