Signature of Al11Sm3 fragmentsin undercooled Al90Sm10 liquid from ab initio molecular dynamics simulations

Abstract

An ab initio molecular dynamics (MD) simulation is performed to investigate the structural evolution inAl90Sm10 liquid from 1500 to900 K. Development of Al11Sm3 local order upon rapid cooling is suggested by the Honeycutt–Anderson (HA) indexanalysis and the appearance of a predominant Sm–Sm–Sm bond angle around90° when the liquid approaches the melting point (∼920 K). Direct structuralevidence of Al11Sm3 fragments at 900 K is obtained using an atomic cluster alignment methoddeveloped recently. Meanwhile, development of strong icosahedral shortrange order (ISRO) and a non-negligible amount of fcc-type clusters aroundAl in the system are also observed. These results suggest that fcc Al andAl11Sm3 crystalline phases would compete strongly with the formation of an amorphous phasethat exhibits ISRO in the diffusionless solidification limit upon rapid quenching.