Cooling rate dependence of simulated $\mathrm{C}{\mathrm{u}}_{64.5}\mathrm{Z}{\mathrm{r}}_{35.5}$ metallic glass structure

Using molecular dynamics simulations with embedded atom model potential, we study structural evolution of $\mathrm{C}{\mathrm{u}}_{64.5}\mathrm{Z}{\mathrm{r}}_{35.5}$ alloy during the cooling in a wide range of cooling rates $\gamma \in (1.5\cdot {10}^9,{10}^{13})$ K/s. Investigating short- and medium-range order, we show that structure of $\mathrm{C}{\mathrm{u}}_{64.5}\mathrm{Z}{\mathrm{r}}_{35.5}$ metallic glass essentially depends on cooling rate. In particular, a decrease of the cooling rate leads to a increase of abundances of both the icosahedral-like clusters and Frank-Kasper Z16 polyhedra. The amounts of these clusters in the glassy state drastically increase at the ${\gamma }_{\mathrm{m}\mathrm{i}\mathrm{n}}=1.5\cdot {10}^9$ K/s. Analysing the structure of the glass at ${\gamma }_{\mathrm{m}\mathrm{i}\mathrm{n}}$, we observe the formation of nano-sized crystalline grain of $\mathrm{C}{\mathrm{u}}_2\mathrm{Z}\mathrm{r}$ intermetallic compound with the structure of $\mathrm{C}{\mathrm{u}}_2\mathrm{M}\mathrm{g}$ Laves phase. The structure of this compound is isomorphous with that for ${\rm Cu_5Zr}$ intermetallic compound. Both crystal lattices consist of two type of clusters: Cu-centered 13-atom icosahedral-like cluster and Zr-centered 17-atom Frank-Kasper polyhedron Z16. That suggests the same structural motifs for the metallic glass and intermetallic compounds and explains the drastic increase of the abundances of these clusters observed at ${\gamma }_{\mathrm{m}\mathrm{i}\mathrm{n}}$.