Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1, Building 3, 119991, Moscow, Russia.
Chemistry. 2013 Aug 12;19(33):10945-57. doi: 10.1002/chem.201300317. Epub 2013 Jun 21.
Calculations within the framework of the interacting quantum atoms (IQA) approach have shown that the interactions of the helium atom with both tertiary, tC, and secondary, sC, carbon atoms in the metastable He@adamantane (He@adam) endohedral complex are bonding in nature, whereas the earlier study performed within the framework of Bader's quantum theory of atoms in molecules (QTAIM) revealed that only He---tC interactions are bonding. The He---tC and He---sC bonding interactions are shown to be forced by the high pressure that the helium and carbon atoms exert upon each other in He@adam. The occurrence of a bonding interaction between the helium and sC atoms, which are not linked by a bond path, clearly shows that the lack of a bond path between two atoms does not necessarily indicate the lack of a bonding interaction, as is asserted by QTAIM. IQA calculations showed that not only the destabilization of the adamantane cage, but also a huge internal destabilization of the helium atom, contribute to the metastability of He@adam, these contributions being roughly equal. This result disproves previous opinions based on QTAIM analysis that only the destabilization of the adamantane cage accounts for the endothermicity of He@adam. Also, it was found that there is no homeomorphism of the ρ(r) and -v(r) fields of He@adam. Comparison of the IQA and QTAIM results on the interactions in He@adam exposes other deficiencies of the QTAIM approach. The reasons for the deficiencies in the QTAIM approach are analyzed.
在相互作用量子原子（IQA）方法的框架内进行的计算表明，氦原子与处于亚稳态的 He@adamantane（He@adam）包合物中叔碳（tC）和仲碳（sC）碳原子的相互作用本质上是成键的，而之前在 Bader 的原子分子量子理论（QTAIM）框架内进行的研究表明，只有 He---tC 相互作用是成键的。He---tC 和 He---sC 成键相互作用是由氦原子和碳原子在 He@adam 中相互施加的高压强制产生的。氦原子和 sC 原子之间发生成键相互作用，而它们之间没有键路径，这清楚地表明，两个原子之间没有键路径并不一定意味着没有成键相互作用，这与 QTAIM 断言的相反。IQA 计算表明，不仅是金刚烷笼的不稳定性，而且氦原子的巨大内部不稳定性都有助于 He@adam 的亚稳性，这两个贡献大致相等。这一结果反驳了以前基于 QTAIM 分析的观点，即只有金刚烷笼的不稳定性解释了 He@adam 的吸热性。此外，还发现 He@adam 的 ρ(r) 和 -v(r) 场之间没有同胚。比较 He@adam 中相互作用的 IQA 和 QTAIM 结果揭示了 QTAIM 方法的其他缺陷。分析了 QTAIM 方法缺陷的原因。
