Exploring Li4N and Li4O superalkalis as efficient dopants for the Al12N12 nanocage to design high performance nonlinear optical materials with high thermodynamic stability

Abstract

Abstract The influence of superalkalis (Li4N and Li4O) doping on the structural, electrical, optical and nonlinear optical properties of the Al12N12 nanocage has been theoretically investigated through density functional theory. The research findings show the strong impact of the superalkalis over the Al12N12 nanocage. The doping with a superalkali significantly reduced the HOMO-LUMO energy gap by up to 50.75% compared to the pristine Al12N12 nanocage due to the formation of a new HOMO energy level. All the isomers possess diffuse excess electrons and are electrides in nature. The results also revealed the higher stability (interaction energies of up to −118.49\u202fkcal/mol) and deep ultraviolet transparency of the studied isomers. Furthermore, superalkali doping dramatically enhanced the nonlinear optical response of the Al12N12 nanocage. The largest first hyperpolarizability of 5.7\u202f×\u202f104 au is achieved for isomer A of the Li4N@Al12N12 series. This outstanding increase in the NLO response is attributed to the small transition energies (1.27–2.73\u202feV) and charge transfer from the superalkali towards the nanocage. AIM and NCI analysis were also performed to investigate the nature of intermolecular interactions between the superalkali and Al12N12 nanocage. AIM topological analysis revealed that a closed shell electrostatic interaction is dominant. These findings offer an insight into designing and fabricating nonlinear optical materials with exceptional features for their widespread applications in optoelectronics.