Atomic structure of biodegradable Mg-based bulk metallic glass.

Area of Science:

• Materials Science
• Computational Materials Science
• Biomaterials Engineering

Background:

• Bulk metallic glasses (BMGs) are promising for biomedical applications.
• Magnesium-based BMGs are of particular interest due to their biocompatibility and biodegradability.
• Understanding the atomic structure of Mg-Zn-Ca BMGs is crucial for predicting their performance in vivo.

Purpose of the Study:

• To elucidate the atomic structure of Mg60Zn35Ca5 and Mg72Zn23Ca5 bulk metallic glasses using first-principles molecular dynamics simulations.
• To investigate the local atomic environments and chemical short-range order in these candidate biomedical implant materials.
• To determine if structural differences correlate with observed variations in in-vivo behavior.

Main Methods:

• Highly accurate first-principles molecular dynamics (MD) simulations.
• Analysis of atomic coordination numbers for Mg, Zn, and Ca species.
• Computation of chemical short-range order parameters.
• Identification of common local structural motifs.

Main Results:

• Average coordination numbers were found to be ~13 for Mg, ~11 for Zn, and ~18-19 for Ca.
• Icosahedral motifs were prevalent for Mg and Zn atoms, consistent with typical BMG structures.
• A moderate preference for Zn-Mg and Zn-Ca bonding over Zn-Zn bonding was observed.
• No statistically significant structural differences were detected between the Mg60Zn35Ca5 and Mg72Zn23Ca5 compositions.

Conclusions:

• The atomic structures of Mg60Zn35Ca5 and Mg72Zn23Ca5 BMGs are similar, characterized by distinct local environments and prevalent icosahedral clusters.
• The observed moderate avoidance of Zn-Zn bonds suggests specific chemical interactions influencing the glass network.
• The lack of significant structural differences between the two compositions implies that variations in in-vivo behavior may arise from factors beyond the static atomic structure, such as surface reactivity or phase evolution.