School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
Phys Chem Chem Phys. 2013 Oct 14;15(38):16214-9. doi: 10.1039/c3cp52922c. Epub 2013 Sep 2.
The basin hopping search algorithm in conjunction with second-order Møller-Plesset perturbation theory is used to determine the lowest energy structures of the radical cation clusters (NH3)n˙(+), (H2O)n˙(+), (HF)n˙(+), (PH3)n˙(+), (H2S)n˙(+) and (HCl)n˙(+), where n = 2-4. The energies of the most stable structures are subsequently evaluated using coupled cluster theory in conjunction with the aug-cc-pVTZ basis set. These cationic clusters can adopt two distinct structural types, with some clusters showing an unusual type of bonding, often referred to as hemibonding, while other clusters undergo proton transfer to give an ion and radical. It is found that proton transfer based structures are preferred by the (NH3)n˙(+), (H2O)n˙(+) and (HF)n˙(+) clusters while hemibonded structures are favoured by (PH3)n˙(+), (H2S)n˙(+) and (HCl)n˙(+). These trends can be attributed to the relative strengths of the molecules and molecular cations as Brønsted bases and acids, respectively, and the strength of the interaction between the ion and radical in the ion-radical clusters.
采用 basin hopping 搜索算法结合二阶 Møller-Plesset 微扰理论，确定了自由基阳离子簇 (NH3)n˙(+)、(H2O)n˙(+)、(HF)n˙(+)、(PH3)n˙(+)、(H2S)n˙(+)和 (HCl)n˙(+)的最低能量结构，其中 n = 2-4。随后，使用耦合簇理论结合 aug-cc-pVTZ 基组评估最稳定结构的能量。这些阳离子簇可以采用两种不同的结构类型，一些簇表现出一种不寻常的键合类型，通常称为半键合，而其他簇经历质子转移形成离子和自由基。研究发现，基于质子转移的结构在 (NH3)n˙(+)、(H2O)n˙(+)和 (HF)n˙(+)簇中更受欢迎，而半键合结构在 (PH3)n˙(+)、(H2S)n˙(+)和 (HCl)n˙(+)中更受欢迎。这些趋势可以归因于分子和分子阳离子分别作为布朗斯台德碱和酸的相对强度，以及离子-自由基簇中离子和自由基之间相互作用的强度。
