Interaction between two rigid molecules for three mesogenic compounds are calculated by atom-atom potential method taking into account Van der Walls' and electrostatic interactions. Stacking, in-plane and overall minimum energy configurations are studied and the most favourable arrangements for the dimers are found. The Van der Waals' interactions are found to be determinant in the dimer stabilization. The stable configurations are compared with the previous data obtained from crystal structure analysis and from X-ray scattering studies in mesophases.