of fully ordered Gay-Berne crystals

A statistical-mechanical model of a molecular crystal is constructed that permits taking account of the influence of vacancies on both the thermodynamic and structural properties without involving any experimental information. The calculations have been carried out for a fee structure with the nearest neighbour Gay-Beme intermolecular potential. The theory shows that the orientational order parameter has values around 0.9 until the loss of the stability of the lattice, which occurs approximately at the reduced temperature k7’/~, = 1.5 and reduced volume u/u, ’ = 1.6. This indicates that the phase is a fully ordered crystal rather than a plastic crystal. 1