Molecular dynamics simulation is performed for linear liquid crystal molecules using a four-site model. The model consists of four Lennard-Jones centers which are bonded together via central potentials in a shish-kebab shape. When the molecules are left under their own vapor pressure, they exhibit isotropic and smectic B phases with no intervening nematic phase. A wall consisting of frozen Lennard-Jones centers is shown to anchor the molecules and to widen the range of the smectic regime. This demonstrates that the model can be used for molecular dynamics studies on liquid crystals in various polymer matrices.