Phonon spectra and phonon linewidths under (a) and (b) compression strains (ε = −0.5%, −1.0%), and under (c) and (d) tensile strains (ε = 0.5%, 1.0%). The large phonon linewidths mainly focus on the Γ point in the high-frequency region (350–400 cm⁻¹) except for ε = −1.0%, which has large phonon linewidths at the Γ point and the midpoint of the Γ − X line in the range of 150–200 cm⁻¹.