Fig. 9: Comparison of the Raman data from Ye et al.33 with the theory results.

Comparison of the theoretically calculated phonon eigenenergies at T = 0 K with the Raman spectra provided by Ye et al.33. The top panel shows the orthorhombic phonon spectrum and the bottom panel the monoclinic phonon spectrum on a linear scale. The theory spectra are obtained at T = 0 K and are in good agreement with the Raman spectrum. Only the first two B2g modes of the orthorhombic geometry differ substantially from their experimental values. This is consistent with these peaks having a significant broadening. The numerals in the experimental plots label the experimentally measured peaks. We assigned those numbers to the corresponding energies from our theory calculations by minimizing the energy differences and following the modes across the transition.