Ab initio investigation of structure, spectrum, aromaticity and electronic properties of C-10 carbon cluster

作者：Wang, Zhao-Qi; Hu, Cui-E; Chen, Xiang-Rong; Cheng, Yan^*; Chen, Qi-Feng

来源：Computational and Theoretical Chemistry, 2017, 1118: 94-106.

DOI：10.1016/j.comptc.2017.09.007

• C-10 cluster
• Infrared spectra
• Canonical molecular orbital
• Aromaticity

The predicted lower energy structures of neutral carbon cluster C-10 are presented by using the particle swarm optimization method in combination with quantum chemistry calculation. Our results describe a wonderful diversity of C-10 configuration with the DFT and MP2 methods. For linear and cyclic clusters, the energy of most stable monocyclic structure with D-5h symmetry is lower by 1.38 kcal/mol than the transition isomers with D-10h symmetry at CCSD(T)/cc-pVTZ level, which is consistent with the previous theoretical results by others. All linear structures of C-10 cluster have been certified as the metastable states at different calculation methods in this work. Simulated infrared spectra reveals that the extensive electron localization exists in the D-10h configuration leading to the decreasing of the number of vibration modes compared with D-5h, configuration. The nucleus independent chemical shift (NICS) calculations indicate that planar C-10 system is a stable aromatic compound and the position used to calculate the aromatic indices can be affected by the most shielding or deshielded location that we employed. The contribution of the delocalized electrons to the pi-aromaticity is identical in C1(a) and C1(b). By the adaptive natural density partitioning (AdNDP) and canonical molecular orbital (CMO) analysis, we know that the highly symmetric structures have more energy degenerate CMOs and 2 center-2 electron bond connection, and monocyclic C-10 cluster is a globally doubly (sigma- and pi-) aromatic compound. Topological analysis and natural bond orbital (NBO) analysis show that there isn't any electrostatic type of interactions in C-10 structures, and much of negative natural valence electron configuration comes from high angular momentum orbitals. According to the electron configurations, the natural hybrid orbital is mainly composed of sp hybrid in the systems. It is worth mentioning that the competition of complicated many body effects plays a significant role in stabilizing the distorted configuration of C-10 cluster. We expect our work can provide more information for further experimental studies.

• 出版日期2017-10-15
• 单位中国工程物理研究院; 中国工程物理研究院流体物理研究所; 四川大学; 重庆师范大学