Investigation of electronic structure and vibrational spectrum of C60 and its various compounds

ABSTRACT INVESTIGATION OF THE ELECTRONIC STRUCTURE AND VIBRATIONAL SPECTRUM OF C60 AND ITS VARIOUS COMPOUNDS TÜTÜNCÜLER, Hayriye Ph.D. in E.P., University of Gaziantep Supervisor: Asst. Prof. Dr. Ramazan Koç August 2000, 113 Pages In this thesis three main properties of Coo molecule are investigated. These are electronic energy levels, normal modes of vibrations, and Jahn-Teller (JT) effect due to electron-vibron interaction for the ionised Coo molecule. The electronic energy levels have been computed by using Hiickel method as a function of bond strength between the atoms in the molecule. The effect of bond strength is investigated and it is seen that the result is satisfactory for all icosahedral complexes. In order to simplify Hiickel matrices, the projection operators and molecular orbitals of icosahedral structure are constructed Vibrational modes of Coo molecule were found by using the force constant model. This model includes bending force constants in addition to the bond stretching force constants and the interaction between the nearest ten neighbour atoms is taken into consideration to get accurate results. The H®(2h©g) Jahn-Teller problem is investigated analytically by developing a new method. It is checked that the method is applicable to all JT problems. The JT problem is then solved by breaking symmetries of icosahedral group into its mmaximal little groups. It is seen that the energy surfaces are located trigonal (D3) or pentagonal (D5) symmetry depending on the coupling strength constant. Several computer programs are developed to calculate electronic energy levels and to solve JT problems. Keywords: Fullerenes, C60, normal modes, Hiickel method, electronic energy level, symmetry breaking, JT effect. IV