Three-dimensional atomic packing in amorphous solids with liquid-like structure.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Understanding the three-dimensional atomic structure of amorphous solids and liquids is crucial but challenging.
• Current knowledge heavily relies on physical models rather than experimental data.

Purpose of the Study:

• To experimentally determine the 3D atomic positions in monatomic amorphous solids.
• To identify dominant atomic motifs and their structural arrangements in these materials.
• To investigate the role of these motifs in the liquid-to-glass transition.

Main Methods:

• Atomic electron tomography was employed to visualize atomic structures in Ta thin films and Pd nanoparticles.
• Molecular dynamics simulations were used to study the behavior of atomic networks in metallic liquids and during cooling.

Main Results:

• Pentagonal bipyramids were identified as the most abundant atomic motifs in amorphous solids.
• These motifs predominantly form pentagonal bipyramid networks with medium-range order, rather than icosahedra.
• Pentagonal bipyramid networks are prevalent in monatomic metallic liquids and evolve into icosahedra upon quenching to the glass state.

Conclusions:

• The study provides experimental 3D atomic resolution insights into amorphous solid structures.
• Pentagonal bipyramid networks are fundamental to both amorphous solids and their liquid precursors.
• Findings pave the way for future research on amorphous-crystalline phase transitions and glass transitions.