Single Transition-Metal-Anchored γ-Graphyne as a Promising Nonlinear Optical Material: A DFT Investigation

Two-dimensional carbon nanomaterials with illustrious nonlinear optical (NLO) performance are highly favored in the fields of advanced optoelectronic and laser protection technologies. Herein, structural stability, electronic characteristics, and NLO responses of a series of transition metals anchored on γ-graphyne (TM@γ-GY, TM = Sc-Zn, Y-Cd, Hf-Hg) were systematically explored by density functional theory calculations. The calculated binding energies confirmed that the TM atoms can be stably anchored at the 12-membered ring pores of γ-GY via strong coordination interactions. The decoration of transition metals distinctly narrows the HOMO-LUMO energy gap of γ-GY, thereby facilitating charge transfer and enhancing the electronic polarizability of the system. Impressively, the static first and second hyperpolarizabilities reach up to 5.36 × 104 and 6.36 × 106 a.u., respectively. Further two-level model analysis unveiled that the narrowed energy gap and enhanced charge transfer are the key factors governing the NLO properties. Notably, Y@γ-GY, Hf@γ-GY, and Sc@γ-GY systems exhibit exceptionally large second-order NLO responses, whereas Mn@γ-GY and Hf@γ-GY display prominent third-order NLO properties. These outcomes render TM@γ-GY configurations promising candidates for high-performance two-dimensional NLO materials.