  In this article we present and compare two different, coarse-grained
approaches to model electrostatic interactions of disc-shaped aromatic
molecules, specifically coronene. Our study builds on previous work [J. Chem.
Phys. 141, 214110 (2014)] where we proposed, based on a systematic
coarse-graining procedure starting from the atomistic level, an anisotropic
effective (Gay-Berne-like) potential capable of describing van-der-Waals
contributions to the interaction energy. To take into account electrostatics,
we introduce, first, a linear quadrupole moment along the symmetry axis of the
coronene disc. The second approach takes into account the fact that the partial
charges within the molecules are distributed in a ring-like fashion. We then
reparametrize the effective Gay-Berne-like potential such that it matches, at
short distances, the ring-ring potential. To investigate the validity of these
two approaches, we perform many-particle Molecular Dynamics (MD) simulations,
focusing on the crystalline phase (karpatite) where electrostatic interaction
effects are expected to be particularly relevant for the formation of tilted
stacked columns. Specifically, we investigate various structural parameters as
well as the melting transition. We find that the second approach yields
consistent results with those from experiments despite the fact that the
underlying potential decays with the wrong distance dependence at large
molecule separations. Our strategy can be transferred to a broader class of
molecules, such as benzene or hexabenzocoronene.
