Atomic structure of biodegradable Mg-based bulk metallic glass

We have used highly accurate first-principles molecular dynamics simulations to elucidate the structure of Mg 60 Zn 35 Ca 5 and Mg 72 Zn 23 Ca 5 bulk metallic glasses, which are candidate materials for biomedical implants; these two compositions exhibit different behaviours when implanted. The environments of each species are different, and average coordination numbers are ∼13 for Mg, ∼11 for Zn and ∼18-19 for Ca. A wide range of local environments were found and icosahedral motifs, often seen in bulk metallic glasses, were among the most common for both Mg and Zn. Through the computation of a chemical short-range order parameter, a moderate avoidance of Zn-Zn bonding over Zn-Mg or Zn-Ca was observed. No statistically significant difference in structure was observed between the two compositions. Very accurate first-principles molecular dynamics simulations of two Mg-Zn-Ca glasses, which are candidate materials for implants, have been performed. Their structure does not strongly depend on composition, and other directions for optimisation of these glasses are discussed.