Theory of Neutral-Ionic Transition in Organic Crystals. III. Effect of the Electron-Lattice Interaction

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Abstract
The effects of the electron-lattice interaction on the neutral-ionic (NI) transition are investigated. First, the degree of the dimerization u and of charge transfer ρ in the ground state are calculated at different values of S (the strength of the electron-lattice interaction). Next, we study the excited states of lattice-relaxed and Franck-Condon types. The neutral-ionic domain wall (NIDW) as well as the soliton structures are the examples of the former. By these considerations we classify the NI transition into three types. By analyzing the value of ρ, we determine the appropriate value of S for TTF-Chloranil, and discuss the optical, magnetic and electrical properties by these excited states.