Analysis of the liquid–cluster state of melts near the melting point

We have analyzed the available data on the transition from equilibrium crystallization of melts of various substances to nonequilibrium explosive crystallization depending on preliminary heating of the liquid phase to temperature $T_{C}^{+}$. Analogously to the liquid-crystal state, superheating interval $\Delta T_{L}^{+}=T_{C}^{+}$-$T_L$ relative to melting temperature $T_L$ is ascribed to the region of existence of a mesophase described by order parameter $Q$. A comparative analysis has been performed for the dependence of the free energy variation on the order parameter for clusters in the mesophase and on the sizes of crystalline nuclei in the metastable region below the melting point.