Sc. Mcgrother et al., THE ISOTROPIC-NEMATIC TRANSITION OF DIPOLAR SPHEROCYLINDERS - COMBINING THERMODYNAMIC PERTURBATION WITH MONTE-CARLO SIMULATION, Molecular physics, 91(4), 1997, pp. 751-756
We attempt to predict the phase behaviour of elongated molecules posse
ssing longitudinal point dipoles by treating the dipolar interaction a
s a perturbation on a reference system consisting of hard spherocylind
ers. Thermal averages of up to the fourth power of the total dipolar i
nteraction are evaluated by Monte Carlo simulation in the NVT ensemble
of the nonpolar spherocylinders over a range of densities spanning th
e isotropic-nematic transition density. From the evaluation of the fir
st two terms in the high-temperature perturbation expansion of the fre
e energy we find that the nematic phase is destabilized relative to th
e isotropic phase (when compared with the non-polar system) as one swi
tches on a weak central dipolar interaction. In contrast, off-centre d
ipoles appear to have a stabilizing effect on the nematic phase for we
ak dipoles, but as the dipole strength increases the nematic is seen t
o be destabilized with respect to the isotropic phase.