Structural relaxation in pure liquids: Analysis of wavenumber dependence within the approach of generalized collective modes

摘要

Wavenumber dependence of structural relaxation in liquids is studied by the method of generalized collectiveudmodes (GCM). A new perturbation approach within the GCM method is proposed and applied in the longwavelenthudlimit in order to obtain analytical expressions for the wavenumber-dependent structural relaxationudand sound dispersion within a simplified three-variable dynamical model. Analytical results are compared withudnumerical study of generalized modes within a more general five-variable dynamical model, which accountsudfor thermal processes in liquids. Numerical results are presented for four thermodynamic points of Lennard-udJones fluid at the reduced temperature T* = 1.71. We discuss the features of non-hydrodynamic process ofudstructural relaxation in different regions of wavenumbers.