First-principles modeling of nonlinear optical properties of C3N4 polymorphs

Using the first-principles method combined with the anharmonic oscillator model, the electronic, linear, and nonlinear optical properties of four C3N4 polymorphs are investigated. The calculations show that the third-order susceptibilities and nonlinear refractive indices increase with the increase of volume of C3N4 polymorphs below 1.5eV, whereas the plasmon frequencies and relativistic nonlinear refractive indices decrease. The obtained results indicate that the spinel C3N4 has some potential applications in nonlinear optics.