ON THE THERMODYNAMIC RELATIONSHIP BETWEEN NANOCRYSTALLINE MATERIALS AND GLASSES

Atomistic computer simulations are used to expose important parallels that exist in the dynamical properties of nanocrystalline materials an d glasses. Both types of heavily disordered, metastable microstructure s exhibit low- and high-frequency lattice-vibrational modes not seen i n the perfect crystal, giving rise to similar thermodynamic properties at low temperatures, most notably a pronounced anomaly in their speci fic heats and a phase transition from the nanocrystalline state to the glass below a critical grain size. The possibility of a reversible, f ree-energy based transition between the two phases indicates that the two share a common configuration phase space below a certain critical grain size (of the order of 1.4 nm for the system studied in this pape r). This result implies the existence of interesting kinetically-induc ed structural phenomena.