Stability of Crystals Against Melting and Vitrification

Abstract

The long-range atomic order of crystalline alloys can be destroyed by a variation of temperature resulting in regular melting or by non-equilibrium solid state processing resulting in glass formation. The destabilization of the crystalline lattice and evolution of the amorphous phase is triggered by a variety of methods including, for example, alloying beyond the equilibrium limit, mechanical deformation, irradiation, thermal annealing of thin film superlattices and application of high pressures. Under local equilibrium conditions, the crystal-to-glass transition exhibits similar features as equilibrium melting, whereas under non-equilibrium conditions catastrophic vitrification can occur at the T_o-temperature extended into the glass forming regime. It is shown that randomly frozen-in impurities or lattice defects cause rounding of the first-order melting transition to an isentropic transition resulting in a triple point between supersaturated crystal, undercooled liquid and glass at the crossover of the ideal glass transition and melting lines.