Figure 4
From: Thermally triggered phononic gaps in liquids at THz scale
Temperature variations of longitudinal and transverse phononic modes calculated from MD simulations at fixed pressure.
(a,b) Longitudinal and transverse ħω dispersions are derived from the maxima of the corresponding current autocorrelation functions. (a) Longitudinal phononic modes experience attenuation. (b) Emergence of low-frequency transverse phononic gap at low temperatures and high-frequency transverse phononic gap at elevated temperatures. Transverse phononic excitations become heavily overdamped upon crossing the Frenkel line (~358 K, P = 0.9 GPa) and (~400 K, P = 0.8 GPa). Below the Frenkel line transverse phononic modes do not propagate any more (b) and high-q longitudinal modes become strongly localized 
as temperature rises (a).
