A thermodynamic and structural analysis of selenium-tellurium melts

The thermodynamic properties of the selenium-tellurium system are analysed in terms of a novel regular solution model with multiple connectivity. The model is an extension of the regular solution model that discriminates between two forms of tellurium atom according to their connectivity (number of first neighbours). In the resulting ternary system, the chemical equilibrium between these two forms of tellurium is taken into account. The model can be solved in either the Bragg-Williams or the quasi-chemical approximation. A very good representation of the thermodynamic properties is obtained. Moreover, the model predicts a temperature and concentration evolution of the number of first neighbours in the liquid in close agreement with independent neutron scattering measurements. As a result, this model provides a simple insight into the mechanisms that are responsible for the complex thermodynamic and structural behaviour of the Se-Te system. (author)