Enhancement of nonlinear optical properties of nanocarbon cluster C₆₀ by aluminum doping

Abstract The search for good nonlinear optical (NLO) materials is of utmost importance in laser technology and optical information science, making it a popular research topic in materials science. It is reported that the introduction of alkali metal Li can enhance the NLO properties of nanocarbon materials. Here, metal Al, which exhibits similar electron transfer characteristics to Li, was used for the first time to enhance the NLO properties of nanocarbon cluster C 60 , which possesses a large delocalized π structure and the highest yield in the fullerene family. Density functional theory calculations in combination with Boltzmann distribution showed that the most thermodynamically stable Al@ I h (1812)‐C 60 exhibited good second‐order NLO properties, which originated from the noncentrosymmetry geometry and one extra delocalized electron on I h (1812)‐C 60 from the 3p shell of inner Al. Density of state analysis indicated that the molecular orbitals of Al@ I h (1812)‐C 60 were primarily formed by I h (1812)‐C 60 with minimal Al participation, and the presence of Al always resulted in an antibonding orbital effect. Bond critical point and electron localization function analyses indicated almost no covalent interaction between Al and I h (1812)‐C 60 . Exohedral functionalization was employed to further stabilize Al@ I h (1812)‐C 60 with radical character, and the infrared spectrum was also analyzed in detail. This study has promising implications for expanding the potential applications of fullerenes in optical devices.