Molecular dynamics (MD) simulation of liquid crystal phase transitions is computationally expensive. In particular, in systems that exhibit first-order phase transitions, such as nematic-isotropic phase transitions, the potential energy gap between the two stable phases becomes large, making it difficult to sample the states around the phase transition region. In this study, we use an extended ensemble method to efficiently sample the states including near phase transition in the system of 5CB, a typical nematic liquid crystal molecule, to analyze the orientational order, and further discuss the liquid crystal phase transitions by the temperature dependence of the free energy.
