Giant NLO response and ultraviolet transparency of superalakalis decorated C₆O₆Li₆ complexes; a DFT perspective

Materials having nonlinear optical (NLO) properties are the demand of optics and optoelectronics fields because of their widespread applications. Keeping in view the applications of NLO materials, some new superalkalis doped C₆O₆Li₆ complexes are introduced in this study having remarkable NLO response. Thermodynamic stability of nonlinear optical materials (NLO) is prime requirement of experimentalists for practical applications. All the considered complexes have high thermodynamic stability. Furthermore, these superalkali doped complexes reveal fabulous electronic properties. Superalkalis shift their outer shell electrons towards the C₆O₆Li₆ nanocluster, which act as diffuse excess electrons. The HOMO-LUMO gaps (H-L E_gap) of superalkali doped complexes are effectively reduced due to shifting of electrons that reveals their conducting properties. NBO charge analysis confirmed electron charge transfer from superalkalis to C₆O₆Li₆ surface. Linear and NLO properties of these complexes are estimated from first order polarizability (α _o) and hyperpolarizability (β _o) parameters. Among all complexes, C₆O₆Li₆.K₃O has the highest first hyperpolarizability (β _o = 6.02 × 10⁵ au). TD-DFT analysis confirmed the ultraviolet transparency of doped complexes. Two level model is used to rationalize the trend of first hyperpolarizability and the internal factors responsible for the enhancement of NLO response.