ELECTRON-INDUCED TRANSITIONS IN MOLECULAR-SOLIDS

The transitions in molecular solids, which are induced by electronic degrees of freedom (charge fluctuations, excited molecules), are considered from a point of view of a competition between direct and indirect energy contributions. The indirect interactions, which follow from electron-vibration (phonon) coupling, have two effects, static and dynamic. The static effect is due to phonon-mediated indirect interactions while the dynamic one results from the electron-mediated interactions. The effects are discussed, first for a dimer of molecules, to clarify microscopic mechanisms of the interactions, than generalization for many-body system is made. The neutral-ionic transitions, stability of solids ''under chemical pressure'' and photo-induced transitions are discussed.