Maier-Saupe and Onsager approaches as limits of the nematic-isotropic phase transition.
Through a virial expansion, the long and small range properties of the interaction between ellipsoidal nematic molecules are put together in a unique approach that combines the essentials of some classical models that describe the nematic-isotropic phase transition. The Lennard-Jones potential that mediates the interaction between the centers of the mass of molecules, the long range Maier-Saupe interaction that favors their alignment and the molecular hard core that hinders their close approximation, as in the Onsager model, are combined in a unique approach that exhibits two phases transitions; the gaseous-liquid transition and the nematic-isotropic phase transition. As a conclusion, the Onsager and Maier-Saupe approaches were considered limits of the actual physical situation.
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Departamento de Fisica, Universidade Estadual de Londrina, Campus Universitario, 86051-970, Londrina (PR), Brazil. simoes@npd.uel.br
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