%0 Book Section %1 statphys23_0174 %A Mryglod, I.M. %A Bryk, T.M. %B Abstract Book of the XXIII IUPAP International Conference on Statistical Physics %C Genova, Italy %D 2007 %E Pietronero, Luciano %E Loreto, Vittorio %E Zapperi, Stefano %K collective correlation dynamics excitations functions glasses liquids mixtures statphys23 time topic-3 %T Phonon-like excitations in liquid mixtures: simple dynamic models, generalized collective mode approach and computer simulations %U http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=174 %X A concept of collective excitations, being one of the most powerful methods in modern physics, has played an important role in dynamics of many-particle systems, in particular in solid state physics. In this report we present simple dynamic models that allow us to study phonon-like excitations in liquid mixtures. The main idea of our treatment is based on a close analogy between phonon normal coordinates in lattice systems and dynamic variables, describing the density and concentration fluctuations in liquids. Such variables, possessing the properties of normal coordinates, are defined rigorously for a general case of multicomponent mixture and form an orthogonal set of dynamic quantities. We derive for them the equations of macroscopic dynamics. If coupling effects between different phonon-like modes are neglected, the spectrum of collective excitations can be obtained analytically. A condition for an experimental observation of phonon-like modes is also derived. Using more sophisticated version of the theory that is based on the generalized collective mode approach we were able to study in details the role of coupling effects depending on the model and state parameters. It is shown that demixing properties play an important role and determine whether phonon-like modes are stable or not in the long-wavelength region. These results are analyzed in comparison with computer simulations performed for several models of binary and ternary mixtures as well as ionic liquids. Both kinds of theories – simplified and sophisticated ones – are testified in our calculations of relative time correlation functions and collective mode spectra. It is shown that a similar approach can be used for the description of dynamical properties in glasses.

@incollection{statphys23_0174, abstract = {A concept of collective excitations, being one of the most powerful methods in modern physics, has played an important role in dynamics of many-particle systems, in particular in solid state physics. In this report we present simple dynamic models that allow us to study phonon-like excitations in liquid mixtures. The main idea of our treatment is based on a close analogy between phonon normal coordinates in lattice systems and dynamic variables, describing the density and concentration fluctuations in liquids. Such variables, possessing the properties of normal coordinates, are defined rigorously for a general case of multicomponent mixture and form an orthogonal set of dynamic quantities. We derive for them the equations of macroscopic dynamics. If coupling effects between different phonon-like modes are neglected, the spectrum of collective excitations can be obtained analytically. A condition for an experimental observation of phonon-like modes is also derived. Using more sophisticated version of the theory that is based on the generalized collective mode approach we were able to study in details the role of coupling effects depending on the model and state parameters. It is shown that demixing properties play an important role and determine whether phonon-like modes are stable or not in the long-wavelength region. These results are analyzed in comparison with computer simulations performed for several models of binary and ternary mixtures as well as ionic liquids. Both kinds of theories – simplified and sophisticated ones – are testified in our calculations of relative time correlation functions and collective mode spectra. It is shown that a similar approach can be used for the description of dynamical properties in glasses.}, added-at = {2007-06-20T10:16:09.000+0200}, address = {Genova, Italy}, author = {Mryglod, I.M. and Bryk, T.M.}, biburl = {https://www.bibsonomy.org/bibtex/29bcfb9e8b18b8a72a4b60e550a68efed/statphys23}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Pietronero, Luciano and Loreto, Vittorio and Zapperi, Stefano}, interhash = {83e99592bf28169eac1f8baffd7985cf}, intrahash = {9bcfb9e8b18b8a72a4b60e550a68efed}, keywords = {collective correlation dynamics excitations functions glasses liquids mixtures statphys23 time topic-3}, month = {9-13 July}, timestamp = {2007-06-20T10:16:13.000+0200}, title = {Phonon-like excitations in liquid mixtures: simple dynamic models, generalized collective mode approach and computer simulations}, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=174}, year = 2007 }