  We perform extensive Monte Carlo simulations of a two-dimensional bent
hard-needle model in both its chiral zig-zag and its achiral bow-shape
configurations and present their phase diagrams. We find evidence for a variety
of stable phases: isotropic, quasi-nematic, smectic-C, anti-ferromorphic
smectic-A, and modulated-nematic. This last phase consists of layers formed by
supramolecular arches. They create a periodic modulation of the molecular
polarity whose period is sensitively controlled by molecular geometry. We
identify transition densities using correlation functions together with
appropriately defined order parameters and compare them with predictions from
Onsager theory. The contribution of the molecular excluded area to deviations
from Onsager theory and simple liquid crystal phase morphology is discussed. We
demonstrate the isotropic--quasi-nematic transition to be consistent with a
Kosterlitz-Thouless disclination unbinding scenario.
