Ab initio investigation of structure, spectrum, aromaticity and electronic properties of C10 carbon cluster

Abstract

The predicted lower energy structures of neutral carbon cluster C10 are presented by using the particle swarm optimization method in combination with quantum chemistry calculation. Our results describe a wonderful diversity of C10 configuration with the DFT and MP2 methods. For linear and cyclic clusters, the energy of most stable monocyclic structure with D5h symmetry is lower by 1.38kcal/mol than the transition isomers with D10h symmetry at CCSD(T)/cc-pVTZ level, which is consistent with the previous theoretical results by others. All linear structures of C10 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 D10h configuration leading to the decreasing of the number of vibration modes compared with D5h configuration. The nucleus independent chemical shift (NICS) calculations indicate that planar C10 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 π-aromaticity is identical in C1a and C1b. 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 C10 cluster is a globally doubly (σ- and π-) aromatic compound. Topological analysis and natural bond orbital (NBO) analysis show that there isn’t any electrostatic type of interactions in C10 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 C10 cluster. We expect our work can provide more information for further experimental studies.