Fig. 8: Comparison of the Raman data from Kim et al.56 with our theory results.
Comparison of the theoretically calculated phonon eigenenergies at T = 0 K with the Raman spectra provided by Kim et al.56. The top panel shows the orthorhombic phonon spectrum and the bottom panel the monoclinic phonon spectrum. Note that peaks 3 and 5 are almost degenerate in energy and peak 5 only appears in the B2g-channel with a much smaller amplitude than peak 3, which appears in the Ag channel. The theory spectra are obtained at T = 0 K and are in good agreement with Raman spectra. Only the first two B2g modes of the orthorhombic geometry (peaks 2 and 5) 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 by Kim et al.56. We assigned those numbers to the corresponding energies from our theory calculations by minimizing the energy differences and following the modes across the transition.
