  Molecular self-assembly on surfaces constitutes a powerful method for
creating tailor-made surface structures with dedicated functionalities. Varying
the intermolecular interactions allows for tuning the resulting molecular
structures in a rational fashion. So far, however, the discussion of the
involved intermolecular interactions is often limited to attractive forces
only. In real systems, the intermolecular interaction can be composed of both,
attractive and repulsive forces. Adjusting the balance between these
interactions provides a promising strategy for extending the structural variety
in molecular self-assembly on surfaces. This strategy, however, relies on a
method to quantify the involved interactions. Here, we investigate a molecular
model system of 3-hydroxybenzoic acid molecules on calcite (10.4) in ultrahigh
vacuum. This system offers both anisotropic short-range attraction and
long-range repulsion between the molecules, resulting in the self-assembly of
molecular stripes. We analyze the stripe-to-stripe distance distribution and
the stripe length distribution and compare these distributions with analytical
expressions from an anisotropic Ising model with additional repulsive
interaction. We show that this approach allows to extract quantitative
information about the strength of the attractive and repulsive interactions.
Our work demonstrates how the detailed analysis of the self-assembled
structures can be used to obtain quantitative insight into the
molecule-molecule interactions.
