Isostructural phase transitions due to core collapse. III. A model for solid mixtures

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Abstract
Our earlier development of a statistical mechanical theory of isostructural phase transitions due to core collapse [J. Chem. Phys. 65, 2161, 2172 (1976)] is extended to the treatment of solid mixtures exhibiting isostructural transitions. Since mixtures in which two solid phases coexist are typically in states of mechanical but not material equilibrium, we consider the theory for states of mechanical equilibrium only, as well as the theory for coexisting phases in true stable thermodynamic equilibrium. Using an extremely simple Hamiltonian model we find good qualitative agreement between the results of a first‐order perturbation theory and the recent experimental results for Ce1−xThx mixtures. In particular, the theory accounts for the experimentally observed decrease in critical temperature with increasing x and for the dependence of the observed resistivity–temperature isobars upon x.