Strain-Assisted Phase Transformation in Two-Dimensional Transition-Metal Dichalcogenides

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional transition-metal dichalcogenides, like molybdenum disulfide (MoS2), are crucial for advanced applications.
• Understanding their mechanical behavior under stress is vital for material design.

Purpose of the Study:

• To investigate strain-induced phase transformation and crack growth in annealed nanocrystalline MoS2.
• To explore the impact of grain size, misorientation, and annealing on MoS2's phase evolution and mechanical properties.

Main Methods:

• Molecular dynamics (MD) simulations were employed to model MoS2.
• Simulations analyzed phase transformation under various stress states in monocrystalline and nanocrystalline MoS2.
• Annealing and quenching cycles were used to study the influence of thermal energy and mechanical stress.

Main Results:

• The 1T phase of MoS2 transforms more readily to a body-centered tetragonal structure under specific strain conditions.
• Single crystalline 1T MoS2 exhibits lower fracture stress but a longer phonon lifetime compared to the 2H phase.
• Nanocrystalline MoS2 showed significant irreversibility in phase transformation after annealing, with inverse pseudo-Hall-Petch effects observed.

Conclusions:

• Phase transformation in MoS2 is intricately linked with crack initiation and propagation.
• The 1T phase demonstrates reduced grain size sensitivity in fracture stress, suggesting potential for enhanced mechanical resilience in nanocrystalline structures.