, has been studied by the method of statistical thermal analysis (STA). It is shown that the melting temperature of solid
phase (Tm) increases non-monotonic from 970 °C due to rise in the preliminary melt overheating, and Tm reaches asymptotically 1010 °C. The equilibrium melting-crystallization temperature (
) has been defined as 989.2 °C. It is also found an extreme dependence of the melt supercooling on its overheating. The two
curves of irregular dependence of nucleation rate on melt supercooling have been plotted at different melt overheating.