Electronic structures, half-metallic and magnetoelectric properties of pure LiZnN, Mn-doped LiZnN and Mn-doped LiZnN with excess and deficient of Li are geometrically optimized and calculated by using first principle density functional theory based on full potential linearized augumented plane wave method. It reveals that doping of Mn leads to a spin polarized impurity band with a spin polarization of 100%. The system exhibits half-metallic ferromagnetism properties, and strong Mn-N covalent bonds are formed. In Li vacancy system, covalent bonds of Mn-N bonds are strongest. Their bond lengths become shorter, and half-metallic is obviously enhanced. Formation energy of the system decrease, which indicates that the structure is more stable. In Li excess system, half-metallic property of the system disappears and becomes metallic. Impurity band width increases and conductivity of the system increases, but interaction of Mn-N bond becomes weaker. It indicates that magnetic and electrical properties of Mn-doped LiZnN new diluted magnetic semiconductor can be regulated separately via Mn isovalent doping and off-stoichiometry. Ground state of Mn doped LiZnN system is ferromagnetic, and net magnetic moment of the system is mainly contributed by Mn atoms. It is found with Heisenberg model that Li vacancy system increases Curie temperature.

With first-principles density functional theory, geometric structures of pure LiMgN, Mn-doped LiMgN, and Mn-doped LiMgN with excess or deficient of Li are geometrically optimized. Electronic structures, magnetic properties, and optical properties were calculated. It shows that Mn doping produces spin polarized impurity bands, which makes materials exhibit half metallic properties. Their properties are affected by stoichiometry of Li. Deficient of Li makes width of impurity band, net magnetic moments and Curie temperature decrease, while half metallic increase. Excess of Li improves width of impurity band, conductivity and Curie temperature, which makes half metallic and band gap decrease. Mn-doped systems have a new dielectric peak in low-energy region, which enhances absorption of low-frequency electromagnetic waves, and shows red-shift. There is an obvious change in complex refractive index function. Energy loss decreases and blue-shift appears only in Li-deficient compound.

Geometrical structures of Cr doped and Cu-Cr co-doped 32-atoms supercell of AlN were optimized with first principles density functional based on full potential augumented plane waves and generalized gradient approximation (GGA). Lattice constant, band structure, electronic density and optical properties were calculated. It indicates that Cr-doped and Cu-Cr co-doped AlN are both half metallic, their band gaps become narrower. Cu-Cr co-doped AlN system has stronger spin polarization effect than Cr doped, and exhibits fine ferromagnetic. Range of optical absorption becomes broader with doping. Co-doping enhances long-wave absorption and energy loss decreases obviously.

Geometrical structure of Ag doped 32-atom super-cell of AlN was optimized with first principle density functional theory based on full potential linearized augumented plane wave method. Electronic structures,magnetic and optical properties were calculated and discussed in detail. It shows that Ag doping makes Ag4 d electrons hybrid with its nearest neighbor N2 p electrons,which introduces impurity bands to form acceptor energy level and realizes p-type doping. The system enhances its conductivity and shows metallic and weak magnetism. Its net magnetic moment is 1.38 μ_в. Mulliken charge population of N-Ag bonds through Ag doping is small and bonds show strong ionic bonding properties. Imaginary part of dielectric function and optical absorption spectrum of the doping system show a new peak in low energy region. Complex refractive index function changes in low energy region. And absorption edge extends to low energy. Doping system enhances long-wave absorption and energy loss decreases obviously.