Raman spectra of MXenes Zr₂X(X=C and N)

We investigate a polarized Raman characterization of Zr₂X (X = C, N), excited by two commonly used laser lines with wavelenghts of 532 nm and 633 nm, based on first principle calculations. The Raman spectra of Zr₂X has two Raman shift peaks which correspond to the degenerate in-plane vibration mode (E_g) and out-of-plane vibration mode (A_1g). Furthermore, we study the polarization angle dependent Raman intensity for both E_g and A_1g modes in parallel and perpendicular configurations for these two materials. We found that the polarization angle dependent Raman intensity is isotropic when the laser line is perpendicular to the Zr₂X plane. There are either only two maxima, or two maxima larger than the other maxima, in the parallel configuration when the laser line is parallel to the Zr₂X plane, which might be useful in identifying the orientation of Zr₂X in experiment. The results show that the locations of the maxima of the polarization angle dependent Raman intensity rarely depend on the exciting laser line, except that of the E_g mode of Zr₂N.