Dependence of the self-diffusion coefficient on the q-gap value in fluids

Abstract

Despite significant progress in condensed matter physics, a systematic and general relationship between collective phenomena and single-particle properties has not been estimated yet. This work establishes a fundamental relationship between a parameter characterizing collective particle dynamics in fluids and the self-diffusion coefficient, which describes the motion of individual particles. It was shown that the self-diffusion coefficient in bulk fluids directly depends on the appearance of the low-frequency branch of the collective excitation spectrum, in particular, on the width of the specific range of the wavevector values in which there are no excitations, which is denoted as the q-gap. Using molecular dynamics simulations, a three-dimensional system of particles interacting via the Lennard-Jones potential near the freezing line were analyzed. To obtain the detailed dispersion relations and q-gap widths, the two-oscillator model was effectively used to analyse the longitudinal and transverse velocity current spectra. It was established that the dependence of the self-diffusion coefficient on the q-gap is linear for the considered model system. We also discuss in detail the intriguing behavior of the considered dependence near the origin, where an abrupt and significant increase of the self-diffusion coefficient appears. The results are of significant importance for various applied industries and scientific fields, including biotechnology, chemical physics, and soft materials science.

Speaker

Konstantin P. Zhukov
Bauman Moscow State Technical University, Moscow, Russia
Russia

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