The liquid crystal phase behaviour of an idealized model, consisting of a linear array of nine soft repulsive spheres, has been studied by Onsager theory with Parsons scaling. Phase transitions have been calculated as a function of the contact distance of the central sphere, sigma(c), with respect to sigma, the contact distance of the other beads. For both the isotropic-nematic and nematic-smectic phase transitions, it exists a sigma* such that, for sigma < sigma(c) < sigma*, the phase transition, at a fixed pressure, occurs at a higher temperature than in the case with sigma(c) = sigma; the opposite happens for sigma(c) > sigma*. These results could be of interest in the field of fullerene containing liquid crystals. (C) 2004 Elsevier B.V. All rights reserved.