Exploring the NLO Properties of Theoretically Designed Cu/Ag/Au‑Doped C₃N₄ Systems through DFT Analysis

Herein to explore nonlinear optical (NLO) properties, nine novel C₃N₄-based compounds have been theoretically developed through doping approach with coinage metals: copper (Cu), silver (Ag), and gold (Au). Every metal series has included three variations containing two, three, or four dopant atoms: (C₃N₄@2Cu, C₃N₄@3Cu, C₃N₄@4Cu, C3N4@2Ag, C3N4@3Ag, C3N4@4Ag, C3N4@2Au, C3N4@3Au, C3N4@4Au). These theoretically design model systems have been investigated with density functional theory (DFT) at the B3LYP/LANL2DZ level to study their electrical, optical, and NLO characteristics. Doping of C₃N₄ with coinage metals (Cu, Ag, Au) led to a noticeable improvement in their optical and electronic characteristics. The pure C3N4 material showed a relatively wide band gap (3.50 eV), an absorption maximum at 383 nm, and lower values of polarizability (α₀ = 479.00 au) and hyperpolarizability (β₀ = 479.10 au). After doping with coinage metals, all doped structures of C3N4 showed a redshift in absorption (λmax = 438–836 nm), narrow band gaps (0.63–2.29 eV), and lower excitation energies (ΔE = 1.39–2.99 eV). Additionally, the doped systems of C3N4 reveal higher transition dipole moments (Δμ). ), static mean polarizability (α_O) lies from 541.81 to 809.99 au, mean first hyperpolarizability (β_O) ranges from 717.45 to 140245.86 au, isotropic (iso) polarizabilities (541.81-809.99 au) and anisotropic (aniso) polarizabilities (407.40-1298.65 au). This project will contribute to the development of theoretically design compounds with excess of electrons. The results of this investigation might affect forthcoming studies on exceptionally well NLO materials and act as valuable benchmarks for chemical compound synthesis.