INCLUSION OF DENSITY VARIATION IN THE LANDAU-DE GENNES THEORY OF THE NEMATIC-ISOTROPIC PHASE-TRANSITION

The Landau-de Gennes model of the nematic-isotropic phase transition with the inclusion of the density change is examined in a simple way. We show how a density dependent term gives various thermodynamic quantities consistent with both experimental results and with an assumed low value of TNI-T*=1 K, where the temperature TNI is the nematic-isotropic transition temperature and T* is the absolute limit of stability of the isotropic phase. We also note that this density dependence does not improve with a high value of (Q*-QNI)/QNI (where Q* and QNI are the values of the uniaxial nematic order parameter at T* and TNI, respectively), obtained in the usual Landau-de Gennes theory of the nematic-isotropic phase transition. © 1995 The American Physical Society.