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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >H·(H_2O)_n clusters: Microsolvation of the hydrogen atom via molecular ab initio gradient embedded genetic algorithm (GEGA)
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H·(H_2O)_n clusters: Microsolvation of the hydrogen atom via molecular ab initio gradient embedded genetic algorithm (GEGA)

机译：H·（H_2O）_n团簇：氢原子的分子从头算坡度嵌入式遗传算法（GEGA）的微溶剂化

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A new version of the ab initio gradient embedded genetic algorithm (GEGA) program for finding the global minima on the potential energy surface (PES) of mixed clusters formed by molecules and atoms is reported. The performance of the algorithm is demonstrated on the neutral H·(H_2O)_n (n = 1-4) clusters, that is, a radical H atom solvated in 1-4 water molecules. These clusters are of a fundamental interest. The solvated hydrogen atom forms during photochemical events in water, or during scavenging of solvated electrons by acids, and transiently exists in biological systems and possibly in inclusion complexes in the deep ocean and in the ice shield of earth. The processes associated with its existence are intriguingly complex, however, and have been the subject of decades-long debates. Using GEGA, we explicate the apparently extreme structural diversity in the H·(H_2O) _n (n = 1-4) clusters. All considered clusters have four basic structural types: type I, where the H radical is weakly coordinated to the oxygen atom of one of the water molecules; type II, where H is weakly coordinated to a H atom of one of the water molecules; type III, consisting of H_2, the OH radical, and n - 1 H_2O molecules; and type IV, consisting of H_3O and n - 1 H_2O. There are myriads of isomers of all four types. The lowest energy species of types I and II are the isoenergetic global minima. H·(H_2O)_n clusters appear to be a challenging case for GEGA because they have many shallow minima close in energy some of which are significantly less stable than the global minimum. Additionally, the global minima themselves have high structural degeneracy, they are only weakly bound, and they are prone to dissociation. GEGA performed exceptionally well in finding both the global and the low-energy local minima that were subsequently confirmed at higher levels of theory.
机译：报告了一种新版本的从头开始梯度嵌入遗传算法（GEGA）程序，该程序用于在由分子和原子形成的混合簇的势能面（PES）上找到全局最小值。该算法在中性H·（H_2O）_n（n = 1-4）簇上，即在1-4个水分子中溶解了一个自由基H原子，证明了该算法的性能。这些集群具有根本的意义。溶剂化的氢原子在水中发生光化学事件时形成，或在被酸清除溶剂化的电子期间形成，并短暂存在于生物系统中，并可能深海和地球的冰层中的包合物中。然而，与它的存在相关的过程非常复杂，并且一直是数十年辩论的主题。使用GEGA，我们解释了H·（H_2O）_n（n = 1-4）簇中的表观极端结构多样性。所有考虑的簇具有四种基本结构类型：I型，其中H自由基与一个水分子的氧原子弱配位; II型，其中H与水分子之一的H原子弱配位; III型，由H_2，OH基和n-1 H_2O分子组成; IV型，由H_3O和n-1 H_2O组成。这四种类型都有无数的异构体。 I型和II型的最低能量种类是等能量的全局最小值。 H·（H_2O）_n团簇对于GEGA似乎是一个具有挑战性的情况，因为它们具有许多能量接近的浅最小值，其中一些能量的稳定性远低于全局最小值。此外，全局最小值本身具有很高的结构简并性，它们之间的关联性很弱，并且易于分离。 GEGA在发现全局和低能耗局部最小值方面表现出色，这些最小值随后在较高的理论水平得到了证实。

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