The Influence of Lattice Vacancy on Electrical and Optical Properties of Mg2Si

A detailed theoretical study on the influence of lattice vacancy on structural and optical properties of the magnesium silicide Mg2Si has been performed based on the first-principles pseudopotential method. The results show that Mg2Si has changed from indirect band gap semiconductor to direct band gap semiconductor because of Mg vacancy. Compared with the dielectric function, absorption coefficient, refractive index, reflectivity and photon conductivity of Mg2Si, those peaks of Mg15Si8 appear from 0 to 1.8 eV. And the loss function’s biggest peak of Mg15Si8 moves to the direction of high energy.