Ab initio investigations of quaterthiophene molecular wire under the interaction of external electric field

A conducting molecular wire, quaterthiophene, has been investigated theoretically at ab initio Hartree-Fock levels by considering the interaction from an external electric field. When the external electric field increases, the single bonds become shorter, the double bonds become longer, and the molecular configuration tends to be more planar. All these features make the molecular wire more conjugated. The molecular electronic structure is sensitive to the electric field as well. With increasing the electric field, the HOMO-LUMO gap decreases. Moreover, the spatial distribution of LUMO moves to the high potential end, whereas HOMO to the low potential end.