Stacking of polycyclic aromatic hydrocarbons as prototype for graphene multilayers, studied using density functional theory augmented with a dispersion term

Abstract

The interlayer pi-pi interaction between finite-size models of graphene sheets was investigated by using a density functional theory method, augmented with an empirical R(-6) term for the description of long-range dispersive interaction; these were calibrated by studying the pi-pi interaction between various benzene dimer configurations and comparing the results with previous calculations. For stacked bilayers (dimers) and multilayers of polyaromatic hydrocarbons, which serve as molecular models of graphene sheets, we found that binding energies and energy gaps are strongly dependent on their sizes, while the stacking order and the number of stacked layers have a minor influence. The remarkably broad variation of the energy gap, ranging from 1.0 to 2.5 eV, due mainly to variation of the model size, suggests the potential of broadband luminescence in the visible range for carbon-based nanomaterials that have pi-pi interacting.

Theoretical study of stability and charge-transport properties of coronene molecule and some of its halogenated derivatives: A path to ambipolar organic-based materials?

“…81,82 As a matter of example, structures of coronene-type molecules are known to gain additional stabilization from C· · ·H interactions between molecules belonging to parallel planes (see Figure 7). Thus, we will concentrate in the following on the most stable arrangement of a pair of coronene molecules, from fully optimized BLYP-D3/def2-SVP calculations, which consists in a staggered stacking with the following displacements of the center of mass in the upper molecule with respect to that in the lower one alongside the in-plane (x, y) and perpendicular (z) axes described in for the (0, b, 0) dimer (central dimer of Figure 7) extracted from the unit cell (the X-ray structure of the coronene crystal was taken from the Crystallography Open Database and processed with the Mercury program 85 ); (v) the difference in the association energy on going from the cost-effective def2-SVP (−24.52 kcal mol −1 ) to the sufficiently large def2-TZVP basis set amounts to 3.7 kcal mol −1 , which thus forces the use of the latter in the following if one aims at estimating further association energies of nanoaggregates; and (vi) our results consistently agree with the findings recently reported in the literature [86][87][88][89][90][91][92] concerning relative molecular orientation and association energy. Since the crystal, or any other, structure data are not available for supramolecularly organised fluorinated derivatives, to the best of our knowledge, we will rely next on this level of theory (BLYP-D3/def2-TZVP) to analyse the stability of the rest of non-covalently bound molecules.…”

Bandgap Engineering of Graphene by Physisorbed Adsorbates

“…Only van der Waals inter actions lead to adsorption while no chemical bond is formed. See Supporting Information and other work [ 21 ] on the inter action of polycyclic aromatic molecules with graphene for further details. Another energetically close local minimum is displayed in Figure 1 e, electrons from the PTCDI π -electron system shift the energy of the PTCDI LUMO.…”

Fluorine tracers for the identification of molecular interaction with porous asphaltene aggregates in crude oil

“…To this date, only a few numerical simulations are available that have investigated the interaction of maltenes and asphaltenes by density functional theory [13,14]. Related studies were carried out for modeling the interaction of aromatics with a graphene surface [15][16][17][18], where graphene can be considered as an idealized approximation of asphaltene. In an experimental low-magnetic field investigation comparing the 1 H relaxation properties of saturated-rich and aromatics-rich oils with those of asphaltene-rich oils [6], a tendency was found towards larger T 1 /T 2 ratios in crude oils containing asphaltene, but with no obvious signature of aromatic maltenes.…”