Condensed Matter Physics, 2007, vol. 10, No. 4(52), p. 481, English
Dynamics of ternary liquid mixtures: Generalized collective modes analysis
(Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 79011 Lviv, Ukraine; Institute of Applied Mathematics and Fundamental Sciences, National Technical University of Lviv, 79013 Lviv, Ukraine)
(Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 79011 Lviv, Ukraine; Institute for Theoretical Physics, Linz University, 4040 Linz, Austria)
A parameter-free generalized collective modes (GCM) approach is applied to the study of longitudinal and transverse dynamics in a ternary Lennard-Jones liquid mixture. Spectra of collective excitations are calculated in a wide range of wavenumbers starting from the hydrodynamic region and up to the range of molecular regime. Several simplified dynamical models are used in order to estimate the origin of branches in the spectra of collective excitations. This analysis, permits to establish a crossover from a "coherent" to "partial" type of collective dynamics in the dispersion laws of propagating collective modes. The "coherent" type of collective dynamics is observed in the hydrodynamic region and is represented by sound modes (in the transverse case - shear waves) and propagating optic-like excitations, while in the range of "partial" dynamics (intermediate and large wavenumbers) the dynamical properties are mainly determined by correlated "partial" motions of particles of each species. Within the GCM scheme used the number of propagating optic-like modes, identified in this study, is simply related to the number of components in a multi-component mixture, and this has a close analogy in the dynamics of solids.
ternary liquid mixtures, collective excitations, optic-like modes, molecular dynamics
05.20.Jj, 61.20.Ja, 61.20.Lc