Molecular dynamics simulations are used to examine the geometrical aspects of the icosahedral ordered structure created in the liquid and glassy phases of metallic glasses. The Zr-Cu alloy system is investigated, as well as a simple model for binary alloys in which the atomic size ratio between alloying components can be changed. In both liquid and glassy phases, we discovered the same nature of icosahedral organisation. The icosahedral clusters can be seen in both liquid and glassy phases. The density of the clusters rapidly increases as the temperature near the glass transition point Tg, and the icosahedral clusters begin to join to one another and create a medium-range network structure. We discovered that the dominating linking pattern in the icosahedral network is a pentagonal bicap with five-fold symmetry, which we discovered by looking at the geometry of connections between clusters. Using the Regge calculus, which was originally used to establish a theory of gravity, we can comprehend the mechanism of the construction and growth of the icosahedral order from a geometrical standpoint. According to the Regge calculus, inserting an atomic size difference between alloying elements can reduce the distortion energy of the pentagonal bicap, while a significant atomic size difference can stabilise the icosahedral network.
Author (s) DetailsMasato Shimono
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan.
Hidehiro Onodera
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan.
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