Influence of alkali metal superoxides on structure, electronic, and optical properties of Be₁₂O₁₂ nanocage: Density functional theory study

The effect of alkali metal superoxides M₃O (M = Li, Na, K) on the electronic and optical properties of a Be₁₂O₁₂ nanocage was studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The energy gaps (E_g) of all configurations were calculated. Generally, the adsorption of alkali metal superoxides on the Be₁₂O₁₂ nanocage causes a decrease of E_g. Electric dipole moment μ, polarizability α, and static first hyperpolarizability β were calculated and it was shown that the adsorption of alkali metal superoxides on Be₁₂O₁₂ increases its polarizability. It was found that the absorption of M₃O on Be₁₂O₁₂ nanocluster improves its nonlinear optical properties. The highest first hyperpolarizability (β ≈ 214000 a.u.) is obtained in the K₃O-Be₁₂O₁₂ nanocluster. The TD-DFT calculations were performed to investigate the origin of the first hyperpolarizabilities and it was shown that a higher first hyperpolarizability belongs to the structure that has a lower transition energy.