with a local site-impurity potential in the framework of the su, schrieffer, and Heeger (SSH) model, both the dopant dependence and the chain-length dependence of the vibrational modes related to charged solitons in a finite trans-polyacetylene chain have been studied. The numerical calcultions showed that the well-known Goldstone mode will be pinned by the dopant potentials as well as by the chhain ends. Two localized modes were found in the acoustic-frequency branch. The results are in agree-ment with the infrared- active vbibrational modes also observed in lightly doped polyacetylene cases. A comparison with the phtoexcitation measurements has been given.

The electron.. electron interactions and the creation energy of a soliton in highly conducting polymers were calculated by using a correlated--basis-function method with a general screening Coulomb potential within the Kronig. Penny. model framework. Our results showed that even when the electron-electron interactions are considered，solitons are still the main charge carriers. The strong long-range electron-electron interaction is seen to reduce the creation energy of a soliton. A comparison with results based on the Hubbard model has been made. The 1imitations of the Hubbard model in this application were discussed.

The vibrational properties of strongly coupled one-dimensional electron-lattice systems are dis-tinct form those of weakly coupled ones. While the weakly coupled systems have only four localized modes around the soliton and there is overlap between acoustic and optical phonon branches, the strongly coupled systems can possess more localized modes, and no overlap exists. In terms of the coupling constant λ, the boundary beween strong and weak coupling is λe=0.2119. The number of localized modes depends on λ, and each localized mode can only exist for a certain region of λ. Then the whole rane [0.2/π] of λ can be divided into seven regions, each of which has a charac-teristic disposition of the localized modes.

Instead of spin electrons or holes, the carriers in polymers are supposed to be spin polarons or spinless bipolarons. Based on the spin diffusion theory and Ohm's law, we studied spin-polarized injection into organic polymers. It was obtained that only spin polarons are responsible for the current spin polarization in a ferromagnetic (FM)/organic system. Effects of the conductivity matching and the interfacial resistances on the current spin polarization were discussed.

The ground and excited state energies of the two-dimensional D−centre have been calculated, respectively, as a function of magnetic field. The critical magnetic field values at which the excited states change from unbound to bound have been found. The optical transition between two bound states is discussed. Numerical results with the hyperspherical approach are in good agreement with those obtained through other intensive numerical methods and those obtained through experiments.