Relationship between diffraction peak, network topology, and amorphous-forming ability in silicon and silica

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Network topology is crucial for understanding disorder in materials.
• Pairwise correlations often miss hidden structural details.
• Covalent network topology provides deeper insights into material structure.

Purpose of the Study:

• Compare the covalent network topology of liquid and solidified silicon (Si) with silica (SiO2).
• Analyze ring size, cavity distributions, and tetrahedral order to understand amorphous-forming ability.
• Explain why silica readily forms amorphous structures, while bulk amorphous silicon is difficult to prepare.

Main Methods:

• Analysis of ring size distributions.
• Cavity volume ratio calculations.
• Tetrahedral order assessment.
• Comparison of topological features in liquid and amorphous states.

Main Results:

• Amorphous silicon (a-Si) exhibits narrower ring size distributions and smaller cavity volume ratios than amorphous silica (a-SiO2).
• Significant topological differences exist between liquid Si and liquid SiO2.
• Topological features correlate with diffraction patterns, explaining amorphous-forming abilities.

Conclusions:

• The AX2 tetrahedral corner-sharing network is key to amorphous-forming ability, ruling out a-Si.
• Elemental materials struggle to form bulk amorphous phases via melt quenching.
• Understanding network topology is vital for designing materials with desired amorphous properties.