Estudo Ab initio de poliaceno dopado com enxofre

Abstract

Recent theoretical studies reported that long polyacene chains exhibit a ferromagnetic ground state and a considerable alternation between single and double bonds. The study of nanostructures with magnetic properties has become relevant in elds such as molecular electronics and spintronics. The main disadvantage of polyacene is the chemical instability because it's structure is highly reactive. Experimental results indicate that only small oligomers, up to heptacene, are stable. We study the electronic structure of polyacene chains substitutionally doped by sulfur. The aim of the present study is to investigate the doping by sulfur at the chain edges and it's in uence on magnetic states. The calculations were based on the Density Functional Theory (DFT) with the hybrid functional B3LYP. Firstly, we adopted a small oligomer to study the e ects of the position and concentration of sulfur on the structure and on the energy gap. Large concentrations of sulfur provoke severe geometric distortions causing signi cant changes on the energy gap. Multiple con gurations of doping were tested by adopting large unit cells, which provide more degrees of freedom to the relaxation of the system. In most cases the di erence of energy per unit cell between the magnetic and non-magnetic states was small (of the