CALCULATION OF THE 2-DIMENSIONAL INFRARED-ACTIVE LOCALIZED MODES OF ASOLITON LATTICE IN TRANSPOLYACETYLENE

Starting from the extensional Su-Schrieffer-Heeger model Hamiltonian c ontaining intrachain e-e interactions, a bond-bending term, and an ext ernal Coulomb potential arising from the interchain-charged solitons a nd counterions, all the two-dimensional vibrational modes around the s oliton lattice are calculated for doping levels from y = 3.33 at. % to y = 16.67 at. %. Thirteen localized vibrational modes are found for d opant concentrations from 3.33 to 13.33 %, in which seven modes are in frared active and correspond with the infrared absorption peaks. No lo calized modes have been found for doping levels above y = 16.67 at. %. In addition, the frequencies of the modes are decreased and their loc alizations are weakened when the dopant concentrations increase.