Symmetry Non-Breaking Phase Transition and Critical Point in Hexagonal Mixed Crystal C70(1-X)C60X.

A four-state pseudospin model for the isomorphous phase transition in mixed crystal C70(1-x)C60x is shown to be equivalent to a two-state Ising model with one state degenerate. The model predicts a metastable disordered phase corresponding to a glassy state. The effect of random fields and random bonds is to drive the system towards the critical point.