The Jahn-Teller Effect in Binary Transition Metal Carbonyl Complexes

Jahn-Teller effect and related phenomena attract considerable attention of researchers during last several decades. In the present chapter aimed at the students and postgraduates first of all, as well as at the beginners in this field, we review thoroughly the main mechanisms underlying the Ham effect (which means quenching of the spin-orbit interaction due to the interaction of the electronic energy levels with the crystal lattice vibrations). To make the chapter complete from the educational and pedagogical points of view, all necessary mathematical equations needed for calculations are derived and explained. It is shown how the effective second-order spin-Hamiltonian can be used for a description of the Ham effect and estimation of the Jahn-Teller stabilization energy. In addition, an alternative method of determining the Jahn-Teller stabilization energy based on the harmonic approximation and geometrical consideration of the adiabatic surfaces of the potential energy of the ground and excited electronic states is described. The chapter is followed by an attachment with the derivation of the Ham reduction factor.