Ultra-stiff metallic glasses through bond energy density design

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Elastic properties of crystalline metals correlate with valence electron density.
• This correlation is observed in metallic glasses but breaks down in metalloid metallic glasses due to predominant covalent bonding.
• The underlying reasons for this breakdown remain unclear.

Purpose of the Study:

• To elucidate the physical origin of ultrahigh stiffness in both metalloid and non-metalloid metallic glasses.
• To establish a new materials design criterion for developing ultra-stiff metallic glasses.

Main Methods:

• High energy X-ray diffraction analysis of melt-spun and thin-film metallic glasses.
• Density functional theory (DFT) based molecular dynamics simulations.
• Analysis of bond energy density as a key material property.

Main Results:

• The ultrahigh stiffness in metallic glasses is primarily governed by bond energy density.
• A novel Co33.0Ta3.5B63.5 material was predicted using bond energy density as a design criterion.
• The predicted material exhibits a high bond energy density (0.94 eV Å⁻³) and bulk modulus (263 GPa), surpassing existing Co-B metallic glasses by 17%.

Conclusions:

• Bond energy density is a more accurate predictor of stiffness in metallic glasses than electron density, especially for covalent-dominated systems.
• This study provides a new pathway for designing ultra-stiff metallic materials.
• The predicted Co-Ta-B material demonstrates the potential of bond energy density as a design principle.