MEAN FIELD-THEORY OF A MODEL ANISOTROPIC POTENTIAL OF RANK HIGHER THAN 2

The model potentials U//i//j equals minus f//L(r//i//j)P//L(cos beta //i//j) with rank L equals 2,4,6,8 have been studied using mean field theory. All the potentials yield a first order orientational phase transition with an entropy change increasing with the rank. The order parameters do not always decrease regularly with increasing J as for the rank L equals 2, Maier-Saupe, case.