Temperature dependent structural properties and bending rigidity of pristine and defective hexagonal boron nitride

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Hexagonal boron nitride (h-BN) is a 2D material with unique electronic and mechanical properties.
• Understanding its thermal and structural behavior is crucial for advanced applications.
• Defects can significantly alter the properties of 2D materials.

Purpose of the Study:

• To investigate the structural and thermodynamical properties of pristine and defective h-BN sheets.
• To analyze the temperature dependence of various properties, including lattice parameter, specific heat, and thermal expansion.
• To study the impact of defects on the mechanical and thermal behavior of h-BN.

Main Methods:

• Atomistic simulations using a tuned Tersoff-type inter-atomic empirical potential.
• Investigation across a wide temperature range.
• Analysis of lattice parameter, radial distribution function, specific heat, thermal expansion coefficient, and height correlation functions.

Main Results:

• Specific heat increases beyond the Dulong-Petit limit at high temperatures, indicating strong anharmonicity.
• Height fluctuations and bending rigidity are strongly temperature-dependent, explained by continuum membrane theory.
• Deviation from harmonic membrane theory observed due to strong anharmonicity in h-BN.
• Variance of height fluctuations increases with defect concentration.

Conclusions:

• h-BN exhibits strong anharmonic behavior at elevated temperatures.
• Defects play a significant role in modifying the thermal and mechanical properties of h-BN sheets.
• The findings provide insights into the behavior of 2D materials under varying thermal conditions and defect concentrations.