Giant negative Poisson's ratio in two-dimensional V-shaped materials

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Two-dimensional (2D) auxetic materials exhibit a negative Poisson's ratio (NPR), expanding in width when stretched lengthwise.
• These materials have potential applications in medicine, advanced composites, and fastening technologies.
• Enhancing the auxetic performance of existing 2D materials is a critical area of research.

Purpose of the Study:

• To explore novel 2D auxetic materials with enhanced negative Poisson's ratios (NPR).
• To investigate the relationship between material geometry and auxetic properties.
• To identify new candidates for high-performance auxetic applications.

Main Methods:

• First-principles calculations were employed to investigate the mechanical properties of various MX monolayers.
• The study focused on materials with a unique V-shaped atomic configuration.
• In-plane negative Poisson's ratios (NPR) were systematically calculated for a range of M (Al, Ga, In, Zn, Cd) and X (P, As, Sb, S, Se, Te) elements.

Main Results:

• Giant in-plane negative Poisson's ratios (NPRs) were demonstrated in V-shaped MX monolayers.
• GaP, GaAs, GaSb, ZnS, and ZnTe monolayers exhibit exceptional all-angle in-plane NPRs.
• The AlP monolayer showed a record-breaking giant NPR of -1.779, the largest reported for any 2D material.

Conclusions:

• The V-shaped geometry of MX monolayers is responsible for their exotic auxetic properties.
• These findings introduce a new family of 2D auxetic materials.
• The study provides valuable insights for designing and tuning the NPR of 2D materials for advanced applications.