Electric field-induced bond length and bandgap tunability for enhanced reactivity of nitride nanorings

Electric-field engineering offers an efficient and reversible route to modulate the properties of low-dimensional nanomaterials. In this work, we present a comprehensive density functional theory (DFT) investigation of the two nitride nanorings, i.e., Al₉N₉ and B₉N₉, under an external electric field applied perpendicular to the ring plane. The influence of the electric field on the structural, electronic, and reactivity-related properties is systematically analyzed. Structural parameters reveal gradual bond elongation, angular distortion, and ring contraction with increasing field strength, indicating enhanced polarization while maintaining overall structural stability. The electronic structure exhibits a clear Stark effect, characterized by a pronounced downward shift of the LUMO and a smooth reduction of the HOMO-LUMO bandgap, confirming tunable semiconducting behavior. A steady increase in dipole moment and a significant shift in the Fermi level demonstrate strong field-induced charge redistribution. Global conceptual DFT descriptors, including chemical potential, hardness, softness, electrophilicity, nucleophilicity, and work function, reveal a controlled decrease in electronic hardness and a gradual enhancement of reactivity under the applied field. The linear and systematic evolution of these descriptors suggests that Al₉N₉ operates within a stable Stark regime without electronic instability. Overall, this study establishes the nitride nanoring as a robust electric-field-tunable inorganic semiconductor, highlighting its potential for applications in nanoelectronics, sensing, and field-controlled molecular devices.