Neutral and charged soliton defects in polyyne chains: self-consistent field calculations of the effect of kink solitons on molecular geometry

Abstract

The effect of neutral and charged soliton defects on the molecular geometry of long polyyne chains has been investigated using self-consistent field (SCF) molecular orbital theory. This lattice kink was found to be relatively compact for neutral and singly charged solitons but considerably more extended for doubly charged solitons in closed-shell ion polyyne chains. The spin-density wave for neutral solitons was slightly more extended than the corresponding lattice kink but its width became identical with that of the lattice kink in ion radical polyyne chains. For charged solitons, the charge-density wave was found to be considerably more extended than either the spin-density wave or the lattice kink. The present SCF results are in good agreement with the general analytical form predicted for kink-soliton solutions by field theory models. The formation energy for isolated soliton-anti-soliton pair production in long even-membered polyyne chains has also been calculated using a multi-electron configuration interaction procedure.