'Triplet-excited region' in polyene oligomers revisited:Pariser-Parr-Pople model studied with the density matrix renormalization group method

摘要

We have carried out density matrix renormalization group calculations on the T_1 state of linear polyenes applying the Pariser-Parr-Pople (PPP) Model.The geometry optimization for the polyene oligomers C_(2n)H_(2n+2) (n=4,5,6,...,15) shows that the S_0 to T_1 excitation region is composed of a soliton-antisoliton pair located symmetrically away from the center of the chain and leads to single-and double-bond interconversions in between.The distance between the soliton and antisoliton centers in T_1 state changes with the length of the chain,contradictory to earlier conclusions obtained with PPP-SDCI or ab initio SCI methods.The inconsistency most possibly comes from the insufficient consideration of the electron correlations in small-scale CI methods.