Abstract
Inspired by recent work on the thermodynamic properties of the Lennard-Jones/spline (LJ/s) fluid, we have considered the transport properties of the simple LJ/s fluid. The binary scattering problem for LJ/s particles was solved numerically, and results were compared to the untruncated LJ fluid. The scattering dynamics are affected both by the restricted range of the LJ/s potential, and the stronger attraction between LJ/s particles at distances between the inflection point of the potential and the cutoff range. At small relative kinetic energies, it was found that the scattering cross section of the LJ/s particles is much smaller than that of the LJ particles. The shear viscosity, thermal conductivity, and the self-diffusion coefficient were calculated from the scattering cross sections by the Chapman-Enskog method, and a six-parameter equation with a worst case accuracy of roughly 1 % over the temperature interval [0.1,1000] in LJ units is provided. The smaller scattering cross section at low kinetic energies leads to transport coefficients of the LJ/s fluid to be greater than those of the LJ fluid at low temperatures, and were all found to be roughly 50 % greater at T = 0.1, which is the lowest temperature considered.
Highlights
Knowledge of the transport properties of fluids is key to understanding a wide range of nonequilibrium behavior, such as thermal conduction, viscous flow, and diffusion
The distance of closest approach and problem, the collision integrals (n,s) needed for calculating the the scattering angle obtained for both Lennard-Jones/spline model (LJ/s) and Lennard-Jones 12-6 potential (LJ) are shown as transport coefficients may be obtained
We have provided an account of the properties of binary scattering events between LJ/s particles and their untruncated LJ counterparts
Summary
Knowledge of the transport properties of fluids is key to understanding a wide range of nonequilibrium behavior, such as thermal conduction, viscous flow, and diffusion. The infinite range of this potential is, the cause of some problems in the application of periodic boundary conditions in direct molecular dynamics simulations. For this reason, the potential is often replaced in practical calculations by a truncated version with a finite range. The potential is often replaced in practical calculations by a truncated version with a finite range One such potential is the Lennard-Jones/spline model (LJ/s) [2], which truncates the potential smoothly by means of a cubic spline. Transport properties of the untruncated Lennard-Jones fluid have been studied for nearly a century, and transport coefficients are known to a high degree of precision over a wide range of temperatures and densities. Highaccuracy calculations are important as the basis for further work, such as the prediction of transport coefficients at higher densities, which will be the topic for a future paper
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