  Recently, a new class of smectic liquid crystal phases (SmCP phases)
characterized by the spontaneous formation of macroscopic chiral domains from
achiral bent-core molecules has been discovered. We have carried out Monte
Carlo simulations of a minimal hard spherocylinder dimer model to investigate
the role of excluded volume interations in determining the phase behavior of
bent-core materials and to probe the molecular origins of polar and chiral
symmetry breaking. We present the phase diagram as a function of pressure or
density and dimer opening angle $\psi$. With decreasing $\psi$, a transition
from a nonpolar to a polar smectic phase is observed near $\psi = 167^{\circ}$,
and the nematic phase becomes thermodynamically unstable for $\psi <
135^{\circ}$. No chiral smectic or biaxial nematic phases were found.
