Molecular dynamics studies of short to medium range order in Cu ₆₄Zr₃₆ metallic glass

For metallic glasses, the cluster packing scheme addresses mainly the low solute concentration regime and it breaks down beyond a length scale of a few clusters. In the present work, from the viewpoint of core-shell structure rather than cluster packing, short- and medium-range orders in Cu₆₄Zr ₃₆ metallic glass were investigated using the large-scale atomic/molecular massively parallel simulator. In the first three coordination shells, the total number of atoms within the nth coordination shell is 13, 61, and 169. And the number of atoms on the nth coordination shell is 12n ². Besides, the basic atomic structure could be obtained from a central icosahedron surrounded by a shell of 12n² atoms. From the fourth coordination shell on, the total number of atoms is 307, 561, and 924, respectively, consistent with that in an icosahedral shell structure. Our finding suggests that for the optimum glass former in the Cu-Zr binary system, the basic atomic structures over both short- and medium-range length scales have the characteristics of an icosahedral shell structure.