Quantum-Chemical and Quantum-Graph Models of the Dynamical Structure of CH₅⁺

Experimental and computational results about the structure, dynamics, and rovibrational spectra of protonated methane have challenged a considerable number of traditional chemical concepts. Hereby theoretical and computational results are provided about the dynamical structure of CH5+. It is shown that the ground vibrational state investigated thus far by computations, forbidden by nuclear-spin statistics, has a structure similar to the first allowed vibrational state and, in fact, the structures of all vibrational states significantly below 200 cm-1 are highly similar. Spatial delocalization of the nuclei, determined by nuclear densities computed from accurate variational vibrational wave functions, turns out to be limited when viewed in the body fixed frame, confirming that the effective structure of CH5+ is well described as a CH3+ tripod with a H2 unit on top of it. The interesting and unusual qualitative aspects of the sophisticated state dependent variational results receive full explanation via simple quantum-graph models.