Lattice Engineering Novel 2D Monolayer in Zinc Pnictides

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Two-dimensional (2D) materials offer unique electronic and mechanical properties.
• Zinc pnictides (ZnX) are compounds with potential for novel material applications.
• Understanding the stability of 2D monolayers is crucial for their synthesis and application.

Purpose of the Study:

• To systematically investigate the structural, electronic, and thermodynamic stabilities of 2D monolayers of IIB-VA zinc pnictides (ZnX, where X = As, Sb, Bi).
• To identify the most stable 2D monolayer structure among various geometries.
• To explore the electronic properties, dynamical stability, and potential auxetic behavior of the identified stable monolayer.

Main Methods:

• Utilized density functional theory (DFT) with the HSE06 hybrid functional for accurate calculations.
• Modeled 2D monolayers (2D-L1, L2, L3) derived from 3D bulk ZnX structures.
• Employed lattice engineering and compared various symmetries (tetragonal, hexagonal, wurtzite).
• Performed phonon dispersion calculations and *ab initio* molecular dynamics (AIMD) for stability analysis.

Main Results:

• The 2D-L1 monolayer with rectangular symmetry was identified as the ground-state and dynamically stable structure for ZnX compounds at zero strain.
• The 2D-L1 monolayer exhibits wider band gaps compared to their bulk counterparts, with direct band gaps in ZnSb and ZnBi.
• ZnAs 2D-L1 monolayer shows a negative Poisson's ratio, indicating auxetic properties.

Conclusions:

• The 2D-L1 monolayer represents a thermodynamically and dynamically stable structure for zinc pnictides.
• These findings suggest a potential synthesis route for novel 2D materials with tunable electronic and mechanical properties.
• The auxetic property of ZnAs 2D-L1 opens avenues for applications in advanced materials design.