Bond length order parameter of conjugated polymers
نویسندگان
چکیده
It is usually assumed that the ground state lattice con"guration of polyacetylene is a dimerized chain. We found that the energy can be further reduced by an overall chain length contraction, which leads to a new bond length order parameter, in addition to the well-known bond alternation order parameter. For quasi-particles like solitons and polarons, these two order parameters are coupled with the electron wave functions and vary in space. We generalize the Takayama}Liu}Maki equations in the continuum limit to incorporate this new order parameter. Signi"cant modi"cations are found for the polaron solution. Polyacene, a ladder polymer, is also studied with the inclusion of the bond length order parameter. The ground state is predicted to be a non-alternating structure, with zero energy gap and unusually high electric conductivity. ( 1999 Elsevier Science B.V. All rights reserved.
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