Short-range and medium-range order in Ca7 Mg3 metallic glass

Abstract

A molecular dynamics simulation has been performed on the rapid quenching processes of Ca7 Mg3 alloy including 100 000 atoms. The structures of short-range order (SRO) and medium-range order (MRO) in Ca 7 Mg3 metallic glass are investigated by means of several structural analysis methods. It is found that the SRO in Ca7 Mg 3 metallic glass can be modeled by neither a uniquely prescribed stereo-chemical structure nor five Bernal polyhedra but rather various types of basic clusters in which the icosahedron is dominant. The local energy together with the geometrical constraint plays very important roles in the favorable local structure in metal glasses. The MRO in Ca7 Mg3 metallic glass is characterized by certain types of extended icosahedral clusters combined by intercross-sharing atoms in the form of chains or dendrites, which is different from the fcc or icosahedral building schemes for the MRO in metallic glasses with significant chemical SRO. The size distributions of these MRO clusters present a magic number sequence of 19, 23, 25, 27, 29, 31, 33, 35, 37, 41, 43, and the magic clusters can be classed into three types according to their compactness. © 2010 American Institute of Physics.