Lv Zhen-Long, Xu Kai, Cheng Yan, Chen Xiang-Rong, Cai Ling-Cang
Institute of Atomic and Molecular Physics, College of Physical Science and Technology, Sichuan University, Chengdu 610064, China.
National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900, China.
J Chem Phys. 2014 Aug 7;141(5):054309. doi: 10.1063/1.4891721.
The particle swarm optimization method in conjunction with density functional calculations is used to search the lower energy structures for the cationic water clusters (H2O)5(+). Geometry optimization, vibrational analysis, and infrared spectrum calculation are performed for the most interesting clusters at the MP2/aug-cc-pVDZ level. The relationships between their structural arrangements and their energies are discussed. According to their relative Gibbs free energies, their energy order is determined and four lowest energy isomers are found to have a relative population surpassing 1% below 350 K. Studies reveal that, among these four isomers, one new cluster found here also contributes a lot to the experimental infrared spectrum. Based on topological analysis and reduced density gradient analysis, some meaningful points are found by studying the structural characteristics and the bonding strengths of these cationic water clusters: in the first solvation shell, the central H3O(+) motifs may have a stronger interaction with the OH radical than with the water molecules. The interaction in the second solvation shell may also be stronger than that in the first solvation shell, which is opposite to our intuition.
结合密度泛函计算的粒子群优化方法用于搜索阳离子水簇(H2O)5(+)的低能量结构。在MP2/aug-cc-pVDZ水平上对最有趣的簇进行几何优化、振动分析和红外光谱计算。讨论了它们的结构排列与能量之间的关系。根据它们的相对吉布斯自由能，确定了它们的能量顺序，发现四个最低能量异构体在350 K以下的相对丰度超过1%。研究表明，在这四个异构体中，这里发现的一个新簇对实验红外光谱也有很大贡献。通过对这些阳离子水簇的结构特征和键合强度进行拓扑分析和密度梯度分析，发现了一些有意义的点：在第一溶剂化层中，中心H3O(+)基序与OH自由基的相互作用可能比与水分子的相互作用更强。第二溶剂化层中的相互作用也可能比第一溶剂化层中的相互作用更强，这与我们的直觉相反。
