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The superheating effect, in which a solid is heated well above its melting temperature and remains in an ordered, metastable phase, is a well-known phenomenon in materials science. Superheating can be observed experimentally under carefully controlled conditions, and more routinely in atomistic computer simulations. In the context of simulations of superheating, the so-called Z-method is a recently developed technique which allows a precise characterization of the metastable solid state and the melting temperature. However, metastable states are also present in other first-order phase transitions such as the order–disorder transition in spin systems. In spite of all the available work on the behavior of superheated solids, there have been few attempts to characterize the metastable ordered phase in contexts other than melting. In this work we study the ordered metastable state in a two-dimensional Potts lattice in the microcanonical ensemble under the conditions for first-order transitions. We connect our results with the melting transition in solids, and in particular with the empirical findings of the Z-method. In contrast with the sharp, discontinuous slope of the isochoric curve observed in the melting of solids, an S-shape curve is observed for T ( E ) in the case of spins. We discuss the implications of our results to extend the Z-method and its applicability for general first-order phase transitions. |
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