Soliton spacing in polyacetylene with even carbon-to-dopant ratios

Electron-hole symmetry results in the requirement that if the soliton (S) wavefunction is predominantly on odd sites, the antisoliton (S̄) wavefunction must be predominantly on even ones, or vice versa. Minimum-energy considerations nevertheless dictate that, for polyacetylene doping such that there is an even ratio of CHs to ions, solitons and antisolitons must be evenly spaced, i.e., both must have their centers on sites of the same parity. This requirement can be satisfied by using for either S or S̄ the wavefunction obtained by translation through one site. Such wavefunctions have been studied by Takahashi and Fukutome.