Ab initio quantum force field for simulations of nanostructures

It is demonstrated that the third generation of a recently introduced quantum mechanical polarizable force field (QMPFF) successfully reproduces experimental data on binding energies of polycyclic aromatic hydrocarbons and fullerene ${\mathrm{C}}_{60}$ with graphite. The QMPFF also provides an accurate description of bulk graphite and solid ${\mathrm{C}}_{60}$ properties. In all the studied systems, the electrostatics due to the penetration effect was found to be important and comparable in magnitude with the total interaction energy. The QMPFF predicts graphite exfoliation energy of $55\mathrm{meV}$/atom in agreement with the relatively large experimental value of $52\pm 5\mathrm{meV}$/atom recently suggested by Zacharia et al. [Phys. Rev. B 69, 155406 (2004)].

Figure 1

(Color online) (a) PAHs are presented as fragments of a graphene layer. (b) Electrostatic energy component for PD benzene dimer. QMPFF results (solid red line) are compared with point-charge MMFF94 (Ref. 14) (dashed blue line) and QM data (filled black circles) calculated at second-order Møller-Plesset perturbation theory (MP2) level. (c) Same as (b), but for the total interaction energy. The QM values are the CCSD(T) results (Refs. 18, 19). (d) ES energy calculated with the QMPFF (which is nonzero due to the interpenetration of electron clouds) for a pair of neutral graphite carbons. Open circles correspond to the actual, discrete separations of atoms in adjacent layers.