  We investigate the structural properties of a two-dimensional system of
ellipsoidal particles carrying a linear quadrupole moment in their center.
These particles represent a simple model for a variety of uncharged, non-polar
conjugated organic molecules. Using optimization tools based on ideas of
Evolutionary Algorithms, we first examine the ground state structures as we
vary the aspect ratio of the particles and the pressure. Interestingly, we
find, besides the intuitively expected T-like configurations, a variety of
complex structures, characterized with up to three different particle
orientations. In an effort to explore the impact of thermal fluctuations, we
perform constant-pressure Molecular Dynamics simulations within a range of
rather low temperatures. We observe that ground state structures formed by
particles with a large aspect ratio are in particular suited to withstand
fluctuations up to rather high temperatures. Our comprehensive investigations
allow for a deeper understanding of molecular or colloidal monolayer
arrangements under the influence of a typical electrostatic interaction on a
coarse-grained level.
