Computer simulation is carried out for a system of model liquid crystalline molecules in order to understand the nature of intermolecular interactions responsible for the formation of liquid crystals. The model molecule is made up of linearly connected four spherical beads, each of which acts as a center of the Lennard-Jones interactions. The formation of a nematic phase and the subsequent nematic-isotropic phase transition are observed. It is also found that the liquid crystal formation in a high density system is predominantly driven by repulsive interactions while that in a lower density system requires additional contributions from attractive intermolecular interactions.