THEORETICAL STUDIES OF CHARGED DEFECT STATES IN DOPED POLYACETYLENE AND POLYPARAPHENYLENE.

Defect state calculations were performed for polyacetylene and polyparaphenylene in the framework of the Su, Schrieffer, and Heeger Hamiltonian. In polyacetylene, the study of the energetics of the separation of the radical-ion pair induced upon doping indicates that the two defects tend to remain close to each other. This results in the formation of polarons whose binding energy was estimated to be of the order of 0. 05 ev. Absorption spectra at low doping levels were consistent with polaron formation. Interaction between polarons led to the formation of charged solitons. In poly(p-phenylene), defects were correlated in pairs. Calculations suggest the possibility of bipolarons (doubly charged defects) that yield conductivity without Pauli susceptibility.