Structure of Ca-Mg-Zn Metallic Glasses. (Preprint)

摘要

The amorphous structure of four Ca60MgXZn40-X alloys (X = 10, 15, 20, and 25 at.%) has been modeled using a set of experimental neutron and X-ray scattering data, peak fit analysis, and Reverse Monte Carlo (RMC) simulation. The amorphous structure can be described as a mixture of Mg- and Zn- centered clusters, with Ca dominating in the first coordination shell of these clusters. The coordination number (CN) of 10 (with about 7 Ca and 3 (Mg+Zn) atoms) is the most common for the Zncentered clusters. CN = 11 and 12 (with about 7-8 Ca and 4 (Mg+Zn) atoms) are the most common for the Mg-centered clusters. Fife-fold bond configurations (pentagonal pyramids) dominate (approx. 60%) in the first coordination shell of the clusters, suggesting densely atomic packing. Bond angle distributions suggest the near-equilateral triangles and pentagonal pyramids to be the most common nearest atom configurations. Two Ca-Mg-Zn alloys with inferior GFA have increased amounts of (0,0,12,0), (0,2,8,1), (0,2,8,2) and (0,4,4,3) clusters, which suggests that these clusters may facilitate crystallization.