Figure 1
From: Excitation spectra in fluids: How to analyze them properly
Velocity currents and excitation spectra in a 3D Lennard-Jones fluid. (a) Velocity current spectrum \(C(q,\omega )\) shown in color-coded format (normalized to maximum for each q) at \(T=1.83\) and \(n=1\), dispersion relations \({\omega }_{L,T}(q)\) obtained using single mode analysis (blue rhombs corresponding to longitudinal (LM) and transverse (TM) modes) and the two-oscillator model (red circles), while triangles correspond to \({\omega }_{L,T}\pm {{\rm{\Gamma }}}_{L,T}\). The grey zone corresponds to the region of \(q{n}^{-1/3} < 2\pi /L\) (L is the size of considered system). Panels (b–d) demonstrate sections of the velocity current spectrum at \(q{n}^{-1/3}/\pi =0.5\), 1.0, and 1.5 obtained from MD simulations (symbols) and their fits using the two-oscillator model (5) and single mode analysis with Eq. (4), shown by the solid red and dashed blue lines, respectively. (e–h) Results obtained at \(T=36.41\) and \(n=1\), description is the same as in panels (a–d), respectively.
