Influence of (Li/Na/K) doping and point defect (VAl, Hi) on the magnetic and photocatalytic performance of AlN: A first-principles study

Abstract

Although extensive reports on the influence of Li/Na/K doping on the physical properties of AlN systems exist, the effects of Li/Na/K doping and point defects (VAl, Hi) coexisting in AlN systems on magneto-optical properties are often neglected. Experimentally, Li/Na/K doping and point defects (VAl, Hi) cannot be precisely controlled. In this study, the generalized gradient approximation (GGA) plane wave ultrasoft pseudopotential + U method based on spin density functional theory is adopted to solve the abovementioned problem. The first-principles method is utilized to study the effects of point defects (VAl, Hi) and Li/Na/K doping on the photocatalytic performance of AlN systems. Compared with the Al34MN36 (M = Li/Na/K) system, the Al34MHiN36 (M = Li/Na/K) system presents reduced formation energy and improved stability. The Al34NaHiN36 system has the smallest formation energy and the highest stability. In particular, compared with all doped systems, the Al34NaHiN36 system has the best absorption spectrum redshift, the best carrier activity, the longest carrier lifetime, and the strongest oxidation capacity, that is, the best photocatalytic performance. The first-principles study indicates that N atoms in all Al34MN36 (M = Li/Na/K) and Al34MHiN36 (M = Li/Na/K) systems have acceptor and donor characteristics. The magnetic source of all doped systems is related to the double exchange of carriers as mediators, the itinerant electron polarization of unpaired N2− atoms and electric polarization. This study has certain theoretical guidance for the experimental design and preparation of new AlN magneto-optical functional materials.