  The nematic-isotropic (NI) phase transition of 4-cyano-4'-pentylbiphenyl
(5CB) was simulated using the generalized replica-exchange method (gREM) based
on molecular dynamics simulations. The effective temperature is introduced in
gREM, allowing the enhanced sampling of configurations in the unstable region,
which is intrinsic to the first-order phase transition. The sampling
performance was analyzed with different system sizes and compared with that of
the temperature replica-exchange method (tREM). It was observed that gREM is
capable of sampling configurations at sufficient replica-exchange acceptance
ratios even around the NI transition temperature. A bimodal distribution of the
order parameter at the transition region was found, which is in agreement with
the mean-field theory. In contrast, tREM is ineffective around the transition
temperature owing to the potential energy gap between the nematic and isotropic
phases.
