Graphyne-Derived C₁₂-GR and C₁₆-GY as Potential Nanocapacitor Materials

Graphyne (GY)-derived carbon allotropes such as C₁₂-GR and C₁₆-GY, recently predicted through mechanically induced reconstruction pathways [Kotoko, K. J.; Sodoga, K.; Shaidu, Y.; Seriani, N.; Borah, S.; Beltako, K. Uniaxial Tensile-Induced Phase Transition in Graphynes. J. Phys. Chem. C 2024, 128, 17058], constitute emerging two-dimensional carbon phases with unconventional bonding topologies. In this work, we investigate their structural, electronic, optical, and electrostatic energy-storage properties using first-principles calculations. Both monolayer and AA-stacked bilayer configurations exhibit semi-metallic behavior, accompanied by strong dielectric screening and broadband optical absorption extending from the infrared to the ultraviolet region. The presence of acetylenic linkages in C₁₆-GY enhances the electronic polarizability and increases the density of states near the Fermi level, leading to a stronger response under external electric fields. Under out-of-plane bias, the bilayer systems display reversible field-induced charge accumulation and significant electrostatic energy storage, yielding effective gravimetric capacitance values on the order of ∼100 F/g for C₁₂-GR and above ∼120 F/g for C₁₆-GY within the idealized bilayer capacitor model considered here. These values compare favorably with previously reported theoretical carbon-based nanocapacitor architectures. Overall, the results suggest that mechanically reconstructed GY derivatives may provide promising platforms for nanoscale electrostatic energy storage and nanoelectronic applications.