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Abstract: Using Newtonian and Brownian dynamics simulations, the structural andtransport properties of hard and soft spheres have been studied. The softspheres were modeled using inverse power potentials $V\sim r^{-n}$, with $1-n$the potential softness. Although the pressure, diffusion coefficient andviscosity depend at constant density on the particle softness up to extremelyhigh values of $n$, we show that scaling the density with the freezing pointfor every system effectively collapses these parameters for $n\geq 18$including hard spheres, for large densities. At the freezing points, the longrange structure of all systems is identical, when the distance is measured inunits of the interparticle distance, but differences appear at short distancesdue to the different shape of the interaction potential. This translates intodifferences at short times in the velocity and stress autocorrelationfunctions, although they concur to give the same value of the correspondingtransport coefficient for the same density to freezing ratio; the microscopicdynamics also affects the short time behaviour of the correlation functions andabsolute values of the transport coefficients, but the same scaling with thefreezing density works for Newtonian or Brownian dynamics. For hard spheres,the short time behaviour of the stress autocorrelation function has beenstudied in detail, confirming quantitatively the theoretical forms derived forit.



Author: Erik Lange, Jose B. Caballero, Antonio M. Puertas, Matthias Fuchs

Source: https://arxiv.org/







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