Theoretical study of the non linear optical properties of alkali metal (Li, Na, K) doped aluminum nitride nanocages

Abstract

The effect of alkali metal (Li, Na, and K) doping in aluminum nitride (Al₁₂N₁₂) nanocages is studied through density functional theory (DFT) methods. Six new stable compounds of M@Al₁₂N₁₁ and M@Al₁₁N₁₂ are designed theoretically where alkali metal replaces an atom (Al/N) of a nanocage. The stability of the doped nano-cages is evaluated through binding energy calculations. Doping alkali atom M (M = Li, Na, K) into a nanocage significantly reduces the band gap (HOMO–LUMO gap). Polarizability and first hyperpolarizability are calculated using long range separated methods to evaluate the non-linear optical (NLO) properties of these doped systems. The hyperpolarizability of MAl₁₂N₁₁ nanocages is much higher than that of M@Al₁₁N₁₂ nanocages. The higher hyperpolarizability of M@Al₁₂N₁₁ nanocages is believed to arise from participation of excess diffuse electrons, revealed from PDOS.