Electron structure modelling and investigation of interaction processes for carbon-based-nanoclusters

The electronic structure of C60 has been in the focus of interest of physicists during the last decade. A variety of different theoretical approaches from purely phenomenological to ab initio calculations has been applied to find the electron energy structure and explain main experimental features. Among the experimental data, the high frequency peak (∼ 25 eV) in the response of the cluster calls our attention owing to the self-evident collective nature of the corresponding excitation. It is clear now that the collective electronic excitation of C60 is the surface plasmon mode on the spherical cluster. Any Coulomb-including calculation has to reproduce this feature. However, it is rarely pointed out that mainly the global symmetry (SO(3) spherical topology of the cluster) influences the collective mode. The C60 electron structure symmetry reflects the local triangular symmetry of the graphite-like lattice distorted by the global homology of the curved closed surface. The first will be shown to be of small importance for the plasmon. In relation to this we proposed a quantum mechanical model of spherical shell quantum well (SSQW) for the C60 cluster [1, 2]. We found that electrons freely moving within a thin spherical shell behave as a charged liquid at high enough frequency (see below); for example, the SSQW gives a quantummechanical description of the single cluster plasmon [1]. At high frequencies the spherical surface plasmon determines the optical response of the spherical nano-cluster or the spectrum of electron energy losses [3–5]. That is why it is of interest how the simple hydrodynamic picture accords with the multicomponent nature of the σ and π electron system of the fullerene. The spherical collective mode has a definite angular momentum, hence its electric field is the field of a definite charge multipole. Of course, this simplification fails in the case of a lower symmetry, for example, in a crystal. This means that all spherical single-cluster collective modes have to interact. The plasmon frequency is the highest frequency of the dipole excitation of the total electron density of a quasi-spherical C60 molecule. This mode is triple