Ab initio investigations on three isomers of polyacetylene under the interaction of the external electric field

Abstract

Three isomers of polyacetylene ( trans-transoid polyacetylene (Tt-PA), cis-transoid polyacetylene (Ct-PA), and trans-cisoid polyacetylene (Tc-PA)), as backbones of many conducting molecular wires, in contact with a pair of chemically inert electrodes have been investigated theoretically at the HF/6-31G∗ level by considering the interaction of an external electric field (EF). It is found that the external EF modifies both the geometry and electronic structure of the molecular wires. The application of EF may increase the molecular conjugation and the induced dipole moment, while decrease the HOMO–LUMO gap. It may also make the spatial distributions of the frontier molecular orbitals move from a fully delocalized form to a partially localized one depending on the EF strength. Moreover these changes of three isomers show the structural dependence obviously, the longer the conjugation chain is, the stronger the influence of EF.