Electronic and structural behavior of graphene and azulphene nanoflakes under the influence of two-point charges

Abstract

We have studied the behavior of graphene and azulphene nanoflakes in the presence of two-point charges. The carbon systems geometry was optimized using the DFT method without symmetry constraint. We studied the coronene (7-ring), two azulphene-coronenes (7-ring) with different symmetries, the superbenzene (19-ring), and three azulphene-superbenzenes (19-ring) with also different symmetries and different combinations of five, six, and seven-member rings exposed to an electric field due to two-point charges. In addition, the induced electric dipole and quadrupole were studied as a function of the charge point magnitude and signs.The Stark-lo-Surdo effect in HOMO, LUMO, and total energies was analyzed. The positive (negative) charges decrease (increase) the HOMO, LUMO, and total electronic energies. The contraction and expansion of molecular systems and the induced charge in the molecular plane due to two identical charges were studied. Due to two identical charges, the null net force does not deform the molecular systems out-off the xy-plane at z = 0. Instead, the deformation occurs in the xy-plane at z = 0, and the positive (negative) identical charges expand (contract) the molecular systems. These systems suffer concavation under the presence of the electric field due to two-point charges with opposite signs. The central ring is closer to the positive charge, while the hydrogen atoms belonging to the edges are closer to the negative charge for curved graphene models. The concavation of azulene-based systems is irregular and very intricate.This work aims to generically describe the influence of a pair of ions on the energetic and structural (electronic and geometric) components of two-dimensional carbon nanosystems with five, six, and seven-member rings. Our studies allow understanding of the general behavior to extrapolate to other bidimensional systems with different charge exposition like ions. Despite the complexity of the performance of the electric field due to point charges to systems with many electrons, we can obtain some general behaviors, although difficult to interpret in some cases.