Raman spectrum of MXene Ti 2 C under planar symmetrical strain: First‐principles calculations

The vibrational, electronic and Raman properties of monolayer Ti 2 C under planar symmetrical strain excited by two commonly used laser lines (532 and 633 nm) are investigated by first‐principles calculations. By analyzing the phonon spectrum, the stability of strained monolayer Ti 2 C is obtained. The strained Ti 2 C is found to have the same point group symmetry and thereby the same Raman‐active modes as unstrained Ti 2 C, but their Raman peaks exhibit notable red (blue) shift characteristic with symmetrical tensile (compressive) strain. We also discussed the polarization angle dependent Raman intensity in parallel and perpendicular configuration as a guide for experimental characterization in terms of the locations and magnitudes of maxima and found that the locations of maxima for the E g (A 1g ) mode are dependent (independent) of the laser wavelength and the strain. The variation of the polarization direction averaged Raman spectra versus strain can be further explained by the characteristics of light absorbance.