First-principles of Be/Mg/Ca doping and point defects of VZn and Hi in the magnetic and optical properties of ZnO

Abstract The effects of Be/Mg/Ca doping and the coexistence of Zn vacancies in the magnetic and optical properties of ZnO have been widely reported, but the previous studies have neglected the influence of the H interstitial on the doping system. The source and mechanism of magnetism caused by O ions in the doping system remain unclear, and no reasonable theoretical explanation has been proposed thus far. As a point defect, Zn vacancies are hard to precisely control in experiments. In view of solving this problem, this study uses the first principles under the framework of density functional theory to investigate the effects of the single doping of Be, Mg, and Ca and the coexistence of Zn vacancies and H interstitial in the magnetic and optical properties of ZnO. Findings indicate that the bulk moduli of all doped systems are reduced with respect to that of the undoped Zn36O36. Apart from the O2− ions, some O1− ions exist in all doping systems. The O1− ions containing itinerant electrons are the main source of O ion magnetism in the doping system. The formation energy of the Zn34MHiO36 (M = Be/Mg/Ca) system is lower than that of the Zn34MO36 (M = Be/Mg/Ca) system. Findings indicate that the doping of the H interstitial can reduce the formation energy of the Zn34MO36 (M = Be/Mg/Ca) system, allowing the system to become even more stable. The Zn34BeHiO36 system has the smallest formation energy. The Zn34BeHiO36, Zn34MgHiO36, and Zn34CaHiO36 systems all exhibit magnetism. The carriers’ activity in the photocatalyst, the visible light effect, the separation and lifetime of the carriers, and the photocatalytic oxidation ability are also considered in this research. Compared with the other configurations, the Zn34MgHiO36 system is more stable than the other systems, and it has a longer electron lifetime, stronger electric dipole moment, more obvious absorption spectral red shift, and stronger reduction ability. Therefore, the Zn34MgHiO36 system is the best choice for photocatalysis in H production. This research offers certain theoretical reference value for the design and preparation of new magneto-optical functional materials.