A numerical investigation of the stability of nanometer-sized amorphous structures

Molecular dynamics methods have been employed to investigate the structural stability at 300 K of nanometer-sized particles of a Cu-Mg metallic glass in the size range between 1 and 6 nm. All the particles considered undergo a crystallization process the rate of which depends on the system size. On the contrary, the amorphous structure of the corresponding massive system is stable at 300 K. The final products of the crystallization process of the nanometer-sized particles are similar to the ones obtained from the crystallization of the massive system at 600 K, also studied for comparison. The mechanistic features are instead different and point out a relationship between particle size and crystallization rate. Such relationship indicates that crystallization spontaneously occurs at 300 K only for particles with radius smaller than about 10 nm. In turn, this suggests that a minimum size exists below which the amorphous structure is no longer stable.