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 ${\mathit{T}}_{\mathit{N}\mathit{I}}$-${\mathit{T}}^{\mathrm{*}}$=1 K, where the temperature ${\mathit{T}}_{\mathit{N}\mathit{I}}$ is the nematic-isotropic transition temperature and ${\mathit{T}}^{\mathrm{*}}$ 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 (${\mathit{Q}}^{\mathrm{*}}$-${\mathit{Q}}_{\mathit{N}\mathit{I}}$)/${\mathit{Q}}_{\mathit{N}\mathit{I}}$ (where ${\mathit{Q}}^{\mathrm{*}}$ and ${\mathit{Q}}_{\mathit{N}\mathit{I}}$ are the values of the uniaxial nematic order parameter at ${\mathit{T}}^{\mathrm{*}}$ and ${\mathit{T}}_{\mathit{N}\mathit{I}}$, respectively), obtained in the usual Landau–de Gennes theory of the nematic-isotropic phase transition.

• Received 13 October 1994

DOI:https://doi.org/10.1103/PhysRevE.51.4570