Size effect on atomic structure in low-dimensional Cu-Zr amorphous systems

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Understanding the size-dependent properties of amorphous alloys is crucial for developing advanced materials.
• Previous studies on crystalline alloys show size effects, but less is known about amorphous systems.

Purpose of the Study:

• To investigate the influence of size on the atomic structure and glass transition temperature of Cu64Zr36 amorphous systems.
• To compare the size effects in amorphous particles and films with bulk amorphous materials.

Main Methods:

• Molecular dynamics simulations were employed to model zero-dimensional small-size amorphous particles (SSAPs) and two-dimensional small-size amorphous films (SSAFs).
• Analysis focused on local atomic structure, coordination numbers, bond lengths, packing density, and atomic segregation.
• Glass transition temperatures (Tg) were determined for core and shell components of SSAPs and for SSAFs of varying thicknesses.

Main Results:

• Sample size strongly affects the local atomic structure of Cu64Zr36 SSAPs and SSAFs, creating distinct core and shell regions.
• The shell component of SSAPs exhibits lower average coordination number, longer bond lengths, higher ordering, and lower packing density due to Cu segregation.
• Glass transition temperatures differ significantly between the core (910 K) and shell (577 K) of SSAPs, and Tg decreases with decreasing thickness in SSAFs.

Conclusions:

• Size effects in amorphous Cu64Zr36 systems lead to unique atomic structures and altered thermal properties compared to bulk materials.
• Cu segregation at the surface/shell significantly influences the reduced glass transition temperature observed in nanoscale amorphous systems.
• These findings differ from size effects observed in nanometer-sized crystalline metallic alloys, highlighting the unique behavior of amorphous materials.