Pressure-Driven Atomic Reconstruction Governs Strength Collapse in Slightly Twisted Moiré Diamane Nanostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Moiré engineering and twistronics offer novel ways to control diamane properties.
• Hydrogenated twisted bilayer graphene (tBLG) can transition to moiré diamane.

Purpose of the Study:

• Investigate the pressure-driven phase transition from tBLG to moiré diamane.
• Analyze the impact of twist angles on microstructure, bonding, and mechanical strength.

Main Methods:

• Molecular dynamics (MD) simulations at ambient temperature.
• Analysis of atomic reconstruction, interlayer covalent bonding, and stress distribution.

Main Results:

• Small-angle tBLG (<10°) under pressure forms AA-diamane domains separated by graphene boundaries.
• Decreasing twist angles significantly increases interlayer covalent bonding (up to 82.5% at 2.005°).
• Fracture strength paradoxically decreases with increased diamane bonding (28.2 GPa at 2.005°).

Conclusions:

• Interlayer-bonded diamane domains can unexpectedly reduce the mechanical strength of tBLG.
• Stress concentrations at unbonded graphene boundaries initiate fracture.
• Findings provide insights for tailoring properties of twisted 2D materials.