Superalkalis as a source of diffuse excess electrons in newly designed inorganic electrides with remarkable nonlinear response and deep ultraviolet transparency: A DFT study

Recently, significant progress is observed in the design and synthesis of nonlinear optical materials due to their optoelectronic and biomedical applications. In this report, a series of inorganic electrides (Li ₂ F@Al ₁₂ P ₁₂ , Li ₃ O@Al ₁₂ P ₁₂ and Li ₄ N@Al ₁₂ P ₁₂ ) are designed by doping of Al ₁₂ P ₁₂ nanocluster with superalkalis (Li ₂ F, Li ₃ O and Li ₄ N) and studied through density functional theory (DFT) for their geometrical, electronic and nonlinear optical properties. Computational results indicated that these superalkalis doped complexes possess high stability and low HOMO-LUMO gaps. Interaction energies reveal that adsorption of Li ₄ N on Al _top site of Al ₁₂ P ₁₂ results in highly stable structure (isomer J), where superalkali is strongly chemisorbed on the nanocage (E _int. = −105.13 kcal mol ⁻¹ ). Moreover, the lowest HOMO-LUMO gap is also observed for J isomer of Li ₄ N@Al ₁₂ P ₁₂ (0.44 eV), compared to 0.94 eV for alkali metal doped Al ₁₂ P ₁₂ nanocage and 3.36 eV for pure nanocage. Doping of superalkali on aluminum phosphide nanocage can bring considerable increase in first hyperpolarizabilities (β _o ) response of the nanocage along with deep ultraviolet transparency. The first hyperpolarizability (β _o ) for isomer J of Li ₄ N@Al ₁₂ P ₁₂ is 6.25 × 10 ⁴ au. This study may provide an effective strategy to design high performance NLO materials from stable inorganic electrides.