  The effects of dipolar interactions and molecular flexibility on the
structure and phase behavior of bent-core molecular fluids are studied using
Monte Carlo computer simulations. Some calculations of flexoelectric
coefficients are also reported. The rigid cores of the model molecules consist
of either five or seven soft spheres arranged in a `V' shape with external bend
angle $\gamma$. With purely repulsive sphere-sphere interactions and
$\gamma=0^\circ$ (linear molecules) the seven-sphere model exhibits isotropic,
uniaxial nematic, smectic-A, and tilted phases. With $\gamma \geq 20^\circ$ the
smectic-A phase disappears, while the system with $\gamma \geq 40^\circ$ shows
a direct tilted smectic--isotropic fluid transition. The addition of
electrostatic interactions between transverse dipole moments on the apical
spheres is generally seen to reduce the degree of tilt in the smectic and solid
phases, destabilize the nematic and smectic-A phases of linear molecules, and
destabilize the tilted smectic-B phase of bent-core molecules. The effects of
adding three-segment flexible tails to the ends of five-sphere bent-core
molecules are examined using configurational-bias Monte Carlo simulations. Only
isotropic and smectic phases are observed. On the one hand, molecular
flexibility gives rise to pronounced fluctuations in the smectic-layer
structure, bringing the simulated system in better correspondence with real
materials; on the other hand, the smectic phase shows almost no tilt. Lastly,
the flexoelectric coefficients of various nematic phases -- with and without
attractive sphere-sphere interactions -- are presented. The results are
encouraging, but the computational effort required is a drawback associated
with the use of fluctuation relations.
