Collective excitations in liquid bismuth: the origin of kinetic relaxing modes

Abstract

The origin of relaxing collective modes in liquid semimetallic Bi is studied within the generalized collective modes approach. It is found that the lowest kinetic relaxing mode strongly affects the shape of the density-density time correlation functions beyond the hydrodynamic region and determines specific de Gennes features slowing the density fluctuations near the main peak of the structure factor. It is shown that this kinetic relaxing mode appears due to structural relaxation in a liquid. Contributions of different collective modes to the shape of the density-density time correlation functions are studied in detail.

Longitudinal Dynamics in a Lennard-Jones Binary Liquid: Crossover From Hydrodynamics to the Molecular Regime

“…The short-dashed curve with k 2 -dependence very well fits (see figure 9) the behaviour of this relaxing mode for k < 0.6Å −1 . We note that similar kinetic relaxing process, associated with the structural relaxation phenomenon, has been identified in sim- ple liquids [5,6,20]. In particular, it was found that the corresponding eigenvalues behave in small k range as follows:…”

“…An important point is that, in simple liquids, the structural relaxation process becomes the dominant one beyond the hydrodynamic region and makes the main contribution to the central peak of dynamic structure factor [5,6,20]. In the case of a binary liquid considered one can see in figure 9 that two relaxation processes have nearly comparable relaxation times for k > 1.5Å −1 .…”

Generalized Collective Modes Approach: Mode Contributions to Time Correlation Functions in Liquid Lead

“…However, we point out that the role of relaxing kinetic mode d 2 (k) increases rapidly when k becomes larger. Our recent results, obtained for liquid metallic Cs [14] and a semi-metallic liquid Bi [12], show obviously, that beyond the small-k region the relaxing mode d 2 (k) is the lowest one and this mode makes the leading contribution to the shape of density-density time correlation function for intermediate and large wavenumbers in complete agreement with the results found in this study for liquid Pb.…”

“…The zero-th order sum rule requires that the sum ofĀ − nn (k) andĀ + nn (k) should be finite. At the outer gap boundary, when ω(k) → 0 and σ(k) → σ g in (12), only the asymmetric amplitude diverges, so that we find…”

“…In section III the amplitudes of mode contributions are studied in detail for the density-density and heat-heat time correlation functions. We also discuss the origin of kinetic purely relaxing mode d 2 (k), found in our recent GCM-studies of pure liquids [12][13][14]. The last section contains some concluding remarks.…”