Physical Factors Governing the Amplitude of the Electron Transfer Integral in Mixed-Valence Compounds

This paper first reviews the various methods of calculation of the transfer integral in mixed valence compounds. The different physical effects affecting the electron transfer, namely overlap, through bond delocalization, relaxation and polarization of molecular orbitals, and correlation contributions are described and discussed. Illustrative model problems are proposed, and the ability of the various treatments to incorporate these physical effects is studied.