THE 2D LOCALIZED MODES OF BIPOLARON IN CIS-POLYACETYLENE

The localized vibrational modes around a bipolaron in cis-(CH)x are st udied by using a two-dimensional extension of the SSH model that inclu des the bond-bending term. A number of additional modes have been foun d, compared with the results based on the standard SSH model. The ampl itudes of the two directions (x and y direction) are comparable for mo st of the modes as in the trans-(CH)x case. The number of localized mo des and their frequencies depend not only on the coupling constant, bu t also on the bond-bending term and the parameter t1 in removing the d egeneracy of the ground state.