Connections between Structural Characteristics and Crystal Nucleation of Al-Sm Glasses Near Glass Transition Temperature

A systematic investigation on connections between structural characteristics and crystal nucleation during isothermal devitrification of Al-Sm glasses has been carried out by utilizing molecular dynamics simulations combined with an effective data-driven approach named principal component analysis. The results suggest that icosahedral order dominants the local orders in Al-Sm liquids and glasses, whereas the development of crystal-like clusters has been greatly suppressed. Doping of Sm not only increases the population of ICO in Al-Sm alloys, but also promotes the tendency of isolated ICO clusters interpenetrating into icosahedral medium range order. Based on the calculation of local density (LD) and bond-orientational order parameters (BOO), a distinct decoupling in spatial distributions of fluctuations in BOO and LD is observed, and an obvious lagging of densification behind structural ordering is unveiled. These facts unambiguously evidence that the BOO instead of LD is the determinant factor for the origin of crystal nucleation in Al-Sm glass