We present a simple site-based intermolecular potential model for carbon dioxide (the EPM model). It uses point charges and Lennard-Jones interactions centered at each atom. The model predicts a coexistence curve and critical properties quite close to the experimental values. The EPM model predicts a critical temperature of 313.4 +/- 0.7 K compared with an experimental critical temperature of 304 K. By rescaling the potential parameters of the EPM model to obtain the model denoted as "EPM2", we more accurately reproduce the liquid-vapor coexistence curve. A flexible EPM model with rigid bonds, but a flexible angle exhibits identical coexistence properties to within the sensitivity of our calculations.