Tilt grain boundaries in WS₂ from low to high misorientation angles

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Grain boundaries (GBs) are crucial in 2D materials, with their structure and properties depending on misorientation angles.
• Graphene GBs exhibit flexibility, but transition-metal dichalcogenides (TMDs) like WS2 present complexities due to thickness and polar bonds.

Purpose of the Study:

• To construct and analyze energetic favorable grain boundary models in tungsten disulfide (WS2) monolayers.
• To determine the critical angle differentiating low and high-angle GBs in WS2.
• To understand deformation mechanisms at WS2 GBs.

Main Methods:

• Utilized coincident-site-lattice theory with periodic-boundary conditions to model WS2 GBs.
• Employed first-principles simulations to investigate atomistic structures and energies.
• Identified dislocation core structures and analyzed deformation pathways.

Main Results:

• Constructed energetically favorable WS2 GB models, identifying four low-energy dislocation cores.
• Revealed an intermediate critical angle of approximately 14° for WS2 GBs.
• Demonstrated that structural deformations are dissipated via W-S bond distortions, particularly out-of-plane.

Conclusions:

• WS2 GBs exhibit distinct deformation mechanisms compared to graphene, relying on bond distortions.
• The identified critical angle and deformation pathways are vital for understanding WS2 mechanical properties.
• Findings inform the engineering and application of TMD monolayers.