Dominant biaxial quadrupolar contribution to the nematic potential of mean torque

Within the general quadrupolar model for biaxial nematic liquid crystals, whose potential of mean torque
extends that in the Maier-Saupe theory with two extra interaction terms, we propose a quantitative criterion to
identify the dominant biaxial interaction. We show that the ratio of the biaxial-to-uniaxial and uniaxial-toisotropic
transition temperatures is almost independent of one interaction parameter, thus indicating the other
as dominant. We also show that there is a significant mismatch between the principal orientational order
parameters predicted by the theory and those measured for the biaxial phase of a tetrapode.