Lengthy molecular dynamics simulations are performed to verify the reliability of a model of the 4-n-pentyl-4(')-cyanobiphenyl (5CB) molecule appeared in the literature [C. W. Cross and B. M. Fung, J. Chem. Phys. 101, 6839 (1994)]. At 300 K, the time evolution of the orientational order parameter shows clearly that, when thermodynamic equilibrium is reached, the system is in the isotropic phase. At lower temperatures, however, this model appears to be capable of yielding a nematic phase. A new set of parameters for the intermolecular potential is proposed, such that the system shows a stable nematic phase at 300 K. Orientational properties, correlation functions, and translational diffusion coefficients have been calculated for the new model.