Crystal growth nucleation and Fermi energy equalization of intrinsic spherical nuclei in glass-forming melts

The energy saving resulting from the equalization of Fermi energies of a crystal and its melt is added to the Gibbs free-energy change Delta G(2ls) associated with a crystal formation in glass-forming melts. This negative contribution being a fraction epsilon(ls)(T) of the fusion heat is created by the electrostatic potential energy -U-0 resulting from the electron transfer from the crystal to the melt and is maximum at the melting temperature T-m in agreement with a thermodynamics constraint. The homogeneous nucleation critical temperature T-2, the nucleation critical barrier Delta G(2ls)*/k(B)T and the critical radius R-2ls* are determined as functions of epsilon(ls)(T). In bulk metallic glass forming melts, epsilon(ls)(T) and T-2 only depend on the free-volume disappearance temperature T-0l, and epsilon(ls)(T-m) is larger than 1 (T-0l > T-m/3); in conventional undercooled melts epsilon(ls)(T-m) is smaller than 1 (T-0l > T-m/3). Unmelted intrinsic crystals act as growth nuclei reducing Delta G(2ls)*/k(B)T and the nucleation time. The temperature-time transformation diagrams of Mg65Y10Cu25, Zr41.2Ti13.8Cu12.5Ni10Be22.5, Pd43Cu27Ni10P20, Fe83B17 and Ni melts are predicted using classic nucleation models including time lags in transient nucleation, by varying the intrinsic nucleus contribution to the reduction of Delta G(2ls)*/k(B)T. The energy-saving coefficient epsilon(nm)(T) of an unmelted crystal of radius R-nm is reduced when R-nm << R-2ls*; epsilon(nm) is quantified and corresponds to the first energy level of one s-electron moving in vacuum in the same spherical attractive potential -U-0 despite the fact that the charge screening is built by many-body effects.