Fig. 4: Computed enthalpies and infrared/Raman frequencies versus pressure.
From: Symmetry progression and possible polar metallicity in NiPS3 under pressure
a Relative enthalpies of the \(P\bar{3}\) and P1 phases with respect to C2/m. b, c Comparison between frequencies of computed and experimental b infrared and c Raman modes. For clarity, Au/g (blue) and Bu/g (violet) modes from the C2/m phase and Eu/g (orange) modes from the \(P\bar{3}\) phase are selected for display. The experimental frequencies are overlaid in open circles (cyan). The experimental frequencies were shifted from the theoretical data by 5 and 8 cm−1 in panels b and c, respectively, to overlap the theoretical curves. Frequencies from the C2/m (\(P\bar{3}\)) phase are depicted as solid (dashed) lines below 8 GPa and dashed (solid) lines above 8 GPa.
