Negative Poisson's ratio in 2D life-boat structured crystals

Area of Science:

• Materials Science
• Solid State Physics
• Computational Materials Science

Background:

• Two-dimensional (2D) auxetic materials exhibit a negative Poisson's ratio, expanding laterally under tensile strain.
• Their counter-intuitive behavior is often linked to concave structures and idealized models.
• Understanding the fundamental mechanisms is key to designing novel materials.

Purpose of the Study:

• To systematically analyze the mechanical properties of life-boat structured 2D materials.
• To identify new 2D auxetic materials.
• To elucidate the origin of in-plane negative Poisson's ratio in 2D materials.

Main Methods:

• First-principles calculations were employed to investigate material behaviors.
• Analysis included correlating Poisson's ratio with Young's modulus, cohesive energy, and valence shell electron pair repulsion.
• A comparison of energy restored in bond rotation and stretch was used to develop a discovery algorithm.

Main Results:

• Two novel 2D auxetic materials, δ-arsenic and δ-graphane, were identified.
• Calculated Poisson's ratios were successfully correlated with key material properties.
• A self-consistent explanation for the origin of 2D in-plane negative Poisson's ratio was established.

Conclusions:

• The study successfully identified new auxetic materials and provided a deeper understanding of their behavior.
• An algorithmic route for discovering new auxetic materials was proposed.
• The findings contribute to the rational design of advanced functional materials.